TALL-1 nucleic acid molecules, proteins, receptors and methods of use thereof

ABSTRACT

The amino acid and nucleic acid sequence of a protein expressed by monocytes and macrophages, called TALL-1, are disclosed. Homologues, mimetics and antibodies that bind to TALL-1 are disclosed. Also disclosed is the TALL-1 receptor, and homologues of such receptor. The invention includes methods for regulating the interaction between TALL-1 and its receptor and for identifying compounds capable of such regulation. The invention also includes methods for regulating B lymphocyte proliferation, activation, and/or survival.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

[0001] This application claims priority under 35 U.S.C. §119(e) fromU.S. Provisional Application Serial No. 60/132,892, filed May 6, 1999,entitled, “TNF-Family TALL-1 Proteins, Nucleic Acid Molecules and UsesThereof.” This application also claims priority under 35 U.S.C. §119(e)from U.S. Provisional Application Serial No. ______, which is alsoidentified as Attorney Docket No. 2879-72PROV, filed May 1, 2000,entitled “TALL-1 Nucleic Acid Molecules, Proteins, Receptors and Methodsof Use Thereof”. The entire disclosures of U.S. Provisional ApplicationSerial No. 60/132,892 and U.S. Provisional application Ser. No. ______(Attorney Docket No. 2879-72prov) are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to ligand involved in B lymphocyteactivation and proliferation, TALL-1, and to its receptor, TALL-1receptor. More particularly, the present invention relates to TALL-1 andTALL-1 receptor, to homologues of such proteins, to nucleic acidmolecules encoding such proteins, and to methods of making and usingsuch proteins.

BACKGROUND OF THE INVENTION

[0003] Members of the tumor necrosis factor (TNF) ligand family playimportant roles in various physiological and pathological processes,including cell proliferation, differentiation, apoptosis, modulation ofimmune response and induction of inflammation (Smith et al., (1994),Cell 76:959-962; Grewal et al., (1996), The role of CD40 ligand inimmunity and auto-immunity. Page 125-134. In Immune Tolerance, editors:J. Banchereau, B. Dodet, R. Schwartz, E. Trannoy. Elsevier Press:Paris.; Nataga, (1997), Cell 88:355-365; Baker et al., (1998), Oncogene17:3261-3270; Ashkenazi et al., (1999), Curr. Opin. Cell Biol.11:255-260). At least sixteen members of the TNF ligand family have beenidentified. These include TNF, FasL, Lymphotoxin-α, Lymphotoxin-β,TRAIL/APO-2L, CD27L, CD30L, CD40L, 4-1BBL, OX40L, TRANCE/RANKL, LIGHT,TWEAK, TL1, APRIL/TALL-2 and TALL-1 (Smith et al., (1994), Cell76:959-962; Grewal et al., (1996), The role of CD40 ligand in immunityand auto-immunity. Page 125-134. In Immune Tolerance, editors: J.Banchereau, B. Dodet, R. Schwartz, E. Trannoy. Elsevier Press: Paris.;Nataga, (1997), Cell 88:355-365; Baker et al., (1998), Oncogene17:3261-3270; Ashkenazi et al., (1999), Curr. Opin. Cell Biol.11:255-260; Shu et al., (1999), J. Leukocyte Biology 65:680-683;Schneider et al., (1999), J. Exp. Med. 189:1747-1756; Moore et al.,(1999), Science 285:260-263; Mukhopadhyay et al., (1999), J. Biol. Chem.274:15978-15981). Most TNF family members are synthesized as type IItransmembrane precursors. Their extracellular domains can be cleaved bymetalloproteinases to form soluble cytokines. The soluble andmembrane-bound TNF ligand family members bind to receptors belonging tothe TNF receptor family, which are type I transmembrane proteins withcharacteristic cysteine rich motifs (Smith et al., (1994), Cell76:959-962; Nataga, (1997), Cell 88:355-365; Baker et al., (1998),Oncogene 17:3261-3270; Ashkenazi et al., (1999), Curr. Opin. Cell Biol.11:255-260).

[0004] Members of the TNF family interact with their cognate receptorseither through cell-cell interactions or as soluble proteins after theirextracellular domains are cleaved by metalloproteinases (Smith et al.,(1994), Cell 76:959-962; Nataga, (1997), Cell 88:355-365). The TNFreceptor family contains about 20 members. Stimulation of TNF receptorfamily members by their ligands triggers overlapping and divergentintracellular signal transduction pathways, including those that lead toapoptosis, NF-κB and API activation (Smith et al., (1994), Cell76:959-962; Nataga, (1997), Cell 88:355-365). Therefore regulation ofTNF family members that specifically affect immune responses isdesirable.

[0005] A wide variety of medical treatments require regulation of theimmune response in a patient. Such treatments include, for example,vaccinations, treatments for autoimmune diseases, immunodeficiencydiseases, immunoproliferative diseases, and treatments involving thetransplantation of organs and skin. Traditional reagents and methodsused to regulate a subject's immune response often results in unwantedside effects. For example, immunosuppressive reagents such ascyclosporin A, azathioprine, and prednisone are used to suppress theimmune system of a patient with an autoimmune disease or patientsreceiving transplants. Such reagents, however, suppress a patient'sentire immune response, thereby crippling the ability of the patient tomount an immune response against infectious agents not involved in theoriginal disease. Due to such harmful side effects and the medicalimportance of immune regulation, reagents and methods to regulatespecific parts of the immune system have been the subject of study formany years.

[0006] The present invention can be used to overcome traditionalproblems with immunoregulatory reagents by more specifically regulatingcells, ligands and receptors of the immune system in vivo.

SUMMARY OF THE INVENTION

[0007] The present invention generally relates to TALL-1 nucleic acidmolecules, proteins (including homologues), antibodies, and methods ofmaking and using the same. The present invention also relates to TALL-1receptor nucleic acid molecules, proteins (including homologues),antibodies, and methods of using the same. In particular, the presentinvention relates to methods of regulating the interaction betweenTALL-1 and the TALL-1 receptor to regulate monocyte, macrophage and Blymphocyte mediated immune responses.

[0008] One embodiment of the present invention relates to an isolatedTALL-1 protein. Preferably, the isolated TALL-1 protein comprises anamino acid sequence selected from the group of: (a) SEQ ID NO:2; and (b)a homologue of SEQ ID NO:2. The homologue comprises an amino acidsequence selected from the group of: (i) an amino acid sequence that isat least about 40% identical to SEQ ID NO:2 over at least 175 aminoacids of SEQ ID NO:2; and, (ii) an amino acid sequence that is at leastabout 40% identical to SEQ ID NO:2 over positions 134-285 of SEQ IDNO:2. In a more preferred embodiment, the protein comprises an aminoacid sequence selected from the group of: (a) an amino acid sequencethat is at least about 60% identical to SEQ ID NO:2 over at least 175amino acids of SEQ ID NO:2; and, (b) an amino acid sequence that is atleast about 60% identical to SEQ ID NO:2 over positions 134-285 of SEQID NO:2. In an even more preferred embodiment, the protein comprises anamino acid sequence selected from the group of: (a) an amino acidsequence that is at least about 80% identical to SEQ ID NO:2 over atleast 175 amino acids of SEQ ID NO:2; and, (b) an amino acid sequencethat is at least about 80% identical to SEQ ID NO:2 over positions134-285 of SEQ ID NO:2. In an even more preferred embodiment, theprotein comprises an amino acid sequence selected from the groupconsisting of: (a) an amino acid sequence that is at least about 90%identical to SEQ ID NO:2 over at least 175 amino acids of SEQ ID NO:2;and, (b) an amino acid sequence that is at least about 90% identical toSEQ ID NO:2 over positions 134-285 of SEQ ID NO:2.

[0009] In another embodiment, the isolated TALL-1 protein of the presentinvention has an amino acid sequence comprising at least about 30contiguous amino acids of SEQ ID NO:2. Preferably, the protein has anamino acid sequence comprising at least about 50 contiguous amino acidsof SEQ ID NO:2, and more preferably, at least about 130 contiguous aminoacids of SEQ ID NO:2. In a particularly preferred embodiment, theprotein comprises amino acid residues 134 through 285 of SEQ ID NO:2. Inanother particularly preferred embodiment, the protein comprises anamino acid sequence represented by SEQ ID NO:2.

[0010] In another embodiment, the isolated TALL-1 protein of the presentinvention is encoded by a nucleic acid molecule comprising a nucleicacid sequence that hybridizes under low stringency conditions, andpreferably, moderate stringency conditions, and more preferably, highstringency conditions, to the complement of a nucleic acid sequencerepresented by SEQ ID NO:1. In a particularly preferred embodiment, theprotein is encoded by a nucleic acid molecule comprising a nucleic acidsequence represented by SEQ ID NO:1. In another particularly preferredembodiment, the protein is encoded by a nucleic acid molecule comprisinga nucleic acid sequence represented by nucleotide positions 402 through855 of SEQ ID NO:1.

[0011] In one embodiment of the present invention, an isolated TALL-1protein is soluble. In another embodiment, the isolated TALL-1 proteinis a membrane protein. Preferably, the isolated TALL-1 protein of thepresent invention has TALL-1 biological activity. Such biologicalactivities include, but are not limited to: (a) binding to a TALL-1receptor; (b) costimulation of B lymphocyte proliferation; (c)costimulation of B lymphocyte activation; and/or (d) support of Blymphocyte survival. Preferably, the isolated TALL-1 protein binds to aTALL-1 receptor. In one embodiment, a TALL-1 protein binds to anactivates a TALL-1 receptor. In another embodiment, the TALL-1 proteinis a TALL-1 homologue that does not activate a TALL-1 receptor.

[0012] Yet another embodiment of the present invention relates to anisolated antibody that specifically binds to the isolated TALL-1 proteinof the present invention.

[0013] Another embodiment of the present invention relates to anisolated nucleic acid molecule comprising a nucleic acid sequenceencoding a protein comprising an amino acid sequence selected from thegroup of: (a) SEQ ID NO:2; and, a homologue of SEQ ID NO:2. Thehomologue comprises an amino acid sequence selected from the groupconsisting of: (i) an amino acid sequence comprising at least 130contiguous amino acids of SEQ ID NO:2; and, (ii) an amino acid sequencecomprising at least positions 134-285 of SEQ ID NO:2. Preferably, thehomologue comprises an amino acid sequence comprising at least 150contiguous amino acids of SEQ ID NO:2, and even more preferably, thehomologue comprises an amino acid sequence comprising at least 175contiguous amino acids of SEQ ID NO:2. In a particularly preferredembodiment, the nucleic acid sequence encodes a protein comprising anamino acid sequence represented by SEQ ID NO:2, or a protein comprisingan amino acid sequence comprising amino acids 134-285 of SEQ ID NO:2.

[0014] Preferably, the isolated nucleic acid sequence comprises at least390 contiguous nucleotides of SEQ ID NO:1. In another aspect, thenucleic acid sequence hybridizes under low stringency conditions, andpreferably, moderate stringency conditions, and more preferably, highstringency conditions, to the complement of a nucleic acid sequence SEQID NO:1. In a particularly preferred embodiment, the nucleic acidsequence comprises SEQ ID NO:1, or the nucleic acid sequence comprisesnucleotides 402 through 855 of SEQ ID NO:1.

[0015] One embodiment of the present invention relates to an isolatednucleic acid molecule as set forth above, operatively linked to atranscription control sequence. Another embodiment of the presentinvention relates to a recombinant cell comprising an isolated nucleicacid molecule as set forth above, wherein the cell expresses therecombinant nucleic acid molecule. Yet another embodiment of the presentinvention relates to a recombinant virus, comprising an isolated nucleicacid molecule as set forth above.

[0016] Yet another embodiment of the present invention relates to arecombinant nucleic acid molecule comprising an expression vectoroperatively linked to a nucleic acid molecule comprising a nucleic acidsequence encoding a protein having TALL-1 biological activity. Theprotein comprises an amino acid sequence selected from the group of: (a)SEQ ID NO:2; and, (b) a homologue of SEQ ID NO:2, wherein the homologuecomprises an amino acid sequence selected from the group of: (i) anamino acid sequence that is at least about 40% identical to SEQ ID NO:2over at least 175 amino acids of SEQ ID NO:2; and, (ii) an amino acidsequence that is at least about 40% identical to SEQ ID NO:2 overpositions 134-285 of SEQ ID NO:2.

[0017] Another embodiment of the present invention relates to a methodto produce a TALL-1 protein. Such a method includes the step ofculturing an isolated cell to express any of the recombinant nucleicacid molecules described above, under conditions whereby a TALL-1protein encoded by the recombinant nucleic acid molecule is produced.

[0018] Yet another embodiment of the present invention relates to anisolated TALL-1 receptor homologue, wherein the homologue comprises anamino acid sequence that is: (a) at least about 40% identical to SEQ IDNO:11 over at least 35 amino acids of SEQ ID NO:11; and, (b) less than100% identical to an amino acid sequence selected from the group of SEQID NO:11 and SEQ ID NO:17. In a preferred embodiment, the TALL-1receptor homologue is at least about 65% identical to SEQ ID NO:11, andmore preferably, the homologue is at least about 75% identical to SEQ IDNO:11, and more preferably, the homologue is at least about 90%identical to SEQ ID NO:11. In one embodiment of the present invention,the homologue is less than about 95% identical to the amino acidsequence selected from the group of SEQ ID NO:11 and SEQ ID NO:17; inanother embodiment, the homologue is less than about 90% identical tothe amino acid sequence selected from the group consisting of SEQ IDNO:11 and SEQ ID NO:17.

[0019] In one embodiment, the TALL-1 receptor homologue encoded by anucleic acid molecule comprising a nucleic acid sequence that hybridizesunder moderate stringency conditions to the complement of SEQ ID NO:10,and more preferably, the homologue is encoded by a nucleic acid moleculecomprising a nucleic acid sequence that hybridizes under high stringencyconditions to the complement of SEQ ID NO:10.

[0020] In one embodiment, the TALL-1 receptor homologue binds to TALL-1.In one embodiment, the homologue is a soluble TALL-1 receptor. Inanother embodiment, the homologue does not bind to TALL-1. In anotherembodiment, the homologue activates NF-κB in a cell expressing thehomologue through a TRAF5, TRAF6, NIK, IKKα and IKKβ dependent pathway.In one embodiment, the homologue costimulates B lymphocyte proliferationin a B lymphocyte expressing the homologue.

[0021] Yet another embodiment of the present invention relates to anisolated nucleic acid molecule comprising a nucleic acid sequenceencoding a TALL-1 receptor homologue. The homologue comprises an aminoacid sequence that is: (a) at least about 40% identical to SEQ ID NO:11over at least 35 amino acids of SEQ ID NO:11; and, (b) less than 100%identical to an amino acid sequence selected from the group of SEQ IDNO:11 and SEQ ID NO:17.

[0022] Another embodiment of the present invention relates to acomposition comprising: (a) a compound; and (b) a pharmaceuticallyacceptable carrier. The compound of (a) is selected from the group of:(i) an isolated TALL-1 protein; (ii) an isolated antibody thatselectively binds to the TALL-1 protein of (i); (iii) an isolated TALL-1receptor; and, (iv) an isolated antibody that selectively binds to theTALL-1 receptor of (iii).

[0023] In one aspect of the composition of the present invention, thecompound is an isolated TALL-1 protein. Such a TALL-1 protein can be anyheretofore described TALL-1 protein, including a protein comprising anamino acid sequence selected from the group of: (a) SEQ ID NO:2; and,(b) a homologue of SEQ ID NO:2, wherein the homologue comprises an aminoacid sequence selected from the group of: (i) an amino acid sequencethat is at least about 40% identical to SEQ ID NO:2 over at least 175amino acids of SEQ ID NO:2; and, (ii) an amino acid sequence that is atleast about 40% identical to SEQ ID NO:20 over positions 134-285 of SEQID NO:2. In one embodiment, the isolated TALL-1 protein is encoded by anucleic acid sequence that hybridizes under moderate stringencyconditions to the complement of a nucleic acid sequence encoding SEQ IDNO:2. In another embodiment, the isolated TALL-1 protein comprises anamino acid sequence represented by SEQ ID NO:2.

[0024] In another aspect of he composition of the present invention, thecompound is an isolated TALL-1 receptor. In one embodiment, the receptoris a soluble TALL-1 receptor. In another embodiment, the receptorcomprises an amino acid sequence selected from the group of: (a) SEQ IDNO:11; and, (b) a TALL-1 receptor homologue comprising an amino acidsequence that is: (i) at least about 40% identical to SEQ ID NO:11 overat least 35 amino acids of SEQ ID NO:11; and, (ii) less than 100%identical to an amino acid sequence selected from the group of SEQ IDNO:11 and SEQ ID NO:17.

[0025] Yet another embodiment of the present invention relates to amethod to activate a TALL-1 receptor, comprising contacting a TALL-1receptor with a TALL-1 protein. Preferably, the TALL-1 protein comprisesan amino acid sequence selected from the group of: (a) SEQ ID NO:2; and,(b) a homologue of SEQ ID NO:2, wherein the homologue comprises an aminoacid sequence selected from the group of: (i) an amino acid sequencethat is at least about 40% identical to SEQ ID NO:2 over at least 175amino acids of SEQ ID NO:2; and, (ii) an amino acid sequence that is atleast about 40% identical to SEQ ID NO:2 over positions 134-285 of SEQID NO:2.

[0026] Another embodiment of the present invention relates to a methodto regulate B lymphocyte proliferation, activation, and/or survival,comprising regulating the biological activity of a TALL-1 receptorexpressed by a B lymphocyte. In one aspect, the step of regulatingcomprises inhibiting the biological activity of the TALL-1 receptor. Forexample, the step of regulating can include inhibiting the interactionof TALL-1 with the TALL-1 receptor. In one aspect of this embodiment,the step of inhibiting comprises contacting TALL-1 expressed by amonocyte or macrophage with a compound that inhibits binding of theTALL-1 to the TALL-1 receptor. Such a compound can include, but is notlimited to: (a) an antibody that selectively binds to TALL-1 andinhibits the binding of TALL-1 to the TALL-1 receptor; (b) a solubleTALL-1 receptor; and, (c) a TALL-1 receptor homologue, wherein thehomologue comprises an amino acid sequence that is at least about 40%identical over at least 35 amino acids to SEQ ID NO: II, wherein thehomologue binds to TALL-1, and wherein the receptor does not activateNF-κB when expressed by a cell. In one aspect, the compound ispreferably a soluble TALL-1 receptor.

[0027] In another aspect of this embodiment, the step of inhibitingcomprises contacting the TALL-1 receptor with a compound that inhibitsthe interaction of TALL-1 with the TALL-1 receptor. Such a compound caninclude, but is not limited to: (a) an antibody that selectively bindsto the TALL-1 receptor and inhibits the binding of the TALL-1 receptorby TALL-1; and/or (b) a TALL-1 homologue, wherein the homologuecomprises an amino acid sequence selected from the group of: (i) anamino acid sequence that is at least about 40% identical to SEQ ID NO:2over at least 175 amino acids of SEQ ID NO:2; and, (ii) an amino acidsequence that is at least about 40% identical to SEQ ID NO:2 overpositions 134-285 of SEQ ID NO:2. In this aspect, the homologue binds tothe TALL-1 receptor but does not activate the TALL-1 receptor.

[0028] In another aspect of the method of the present invention, thestep of regulating comprises stimulating the biological activity of theTALL-1 receptor. In one aspect, the method includes the step ofcontacting the TALL-1 receptor with a compound that increases TALL-1receptor activity. Such a compound can include, but is not limited to:(a) an isolated TALL-1 protein; and, (b) an antibody that selectivelybinds to the TALL-1 receptor and activates the receptor. Preferably, theisolated TALL-1 protein comprises an amino acid sequence selected fromthe group of: (a) SEQ ID NO:2; and, (b) a homologue of SEQ ID NO:2,wherein the homologue comprises an amino acid sequence selected from thegroup of: (i) an amino acid sequence that is at least about 40%identical to SEQ ID NO:2 over at least 175 amino acids of SEQ ID NO:2;and, (ii) an amino acid sequence that is at least about 40% identical toSEQ ID NO:2 over positions 134-285 of SEQ ID NO:2.

[0029] In one aspect of the method of the present invention, theregulation of B lymphocyte proliferation, activation and/or survival bythe method is effective to regulate a B-lymphocyte immune response in ananimal. In another aspect of the method of the present invention, theinhibition of B lymphocyte proliferation, activation and/or survival bythe method is effective to inhibit a B lymphocyte-associated autoimmunedisease.

[0030] Yet another embodiment of the present invention relates to amethod to inhibit a B lymphocyte immune response in a patient,comprising inhibiting the interaction of TALL-1 with a TALL-1 receptorin the patient. Another embodiment of the present invention relates to amethod to inhibit a B lymphocyte-associated autoimmune disease in apatient, comprising inhibiting the interaction of TALL-1 with a TALL-1receptor in the patient.

[0031] Yet another embodiment of the present invention relates to amethod to identify compounds that regulate the interaction betweenTALL-1 and a TALL-1 receptor. Such a method includes the steps of: (a)contacting a TALL-1 receptor with a putative regulatory compound; (b)contacting the TALL-1 receptor with a TALL-1 protein comprising an aminoacid sequence selected from the group of: (i) SEQ ID NO:2; and, (ii) ahomologue of SEQ ID NO:2, wherein the homologue comprises an amino acidsequence selected from the group of: (1) an amino acid sequence that isat least about 40% identical to SEQ ID NO:2 over at least 175 aminoacids of SEQ ID NO:2; and, (2) an amino acid sequence that is at leastabout 40% identical to SEQ ID NO:2 over positions 134-285 of SEQ ID NO:2or a homologue of TALL-1; and (c) detecting whether the putativeregulatory compound regulates the TALL-1 receptor. The TALL-1 proteinbinds to and activates the TALL-1 receptor in the absence of theputative regulatory compound. In one aspect, the step of detectingcomprises detecting whether the putative regulatory compound inhibitsthe binding of the TALL-1 protein to the TALL-1 receptor. In anotheraspect, the step of detecting comprises detecting whether the putativeregulatory compound inhibits the activation of the TALL-1 receptor ascompared to in the absence of the putative regulatory compound.

BRIEF DESCRIPTION OF THE FIGURES OF THE INVENTION

[0032]FIG. 1A is an amino acid sequence alignment of human TALL-1 andhuman TALL-2/APRIL.

[0033]FIG. 1B is an amino acid sequence alignment of full-length humanTALL-1 and TALL-2/APRIL with other TNF family members.

[0034]FIG. 2A is a digitized image of a Northern blot analysis showingTall-1 gene expression in human tissues.

[0035]FIG. 2B is a digitized image of an RT-PCR analysis showing Tall-1mRNA expression in isolated primary leukocytes.

[0036]FIG. 3 is a digitized image of a Northern blot analysis showingTall-1 gene expression in U937 and Jurkat cells treated with variousstimulatory agents.

[0037]FIG. 4 is a digitized image of a western blot showing detection ofTALL-1 protein in U937 cells.

[0038]FIG. 5A is a digitized image of a western blot showing expressionof Flag-sTALL-1.

[0039]FIG. 5B is a digitized image of a western blot indicatingpurification of Flag-sTALL-1.

[0040]FIG. 6A is a digitized image of a western blot showing that BCMAinteracts with sTALL-1 but not with sTRAIL.

[0041]FIG. 6B is a digitized image of a western blot showing thatsTALL-1 does not bind to TRAIL receptors.

[0042]FIG. 7A is a flow cytometry histogram showing TALL-1 receptorexpression in various cell lines detected by Flag-sTALL-1.

[0043]FIG. 7B is a flow cytometry histogram showing that BCMA istargeted to plasma membrane where it can bind to sTALL-1.

[0044]FIG. 7C is a flow cytometry histogram showing that sBCMA blocksthe binding of sTALL-1 to its receptor.

[0045]FIG. 8 is a bar graph demonstrating inhibition of TALL-1 triggeredB cell co-stimulation by sBCMA.

[0046]FIG. 9 is a bar graph showing that BCMA activates NF-kB and thatthe activation is potentiated by sTALL-1

[0047]FIG. 10A is a bar graph and digitized image showing the effects ofvarious dominant negative mutants on BCMA-mediated NF-κB activation.

[0048]FIG. 10B is a digitized image of a western blot showing that BCMAinteracts with TRAF5 and TRAF6 but not TRAF2.

DETAILED DESCRIPTION OF THE INVENTION

[0049] The present invention generally relates to isolated nucleic acidsequences encoding TALL-1, to isolated nucleic acid molecules comprisingnucleic acid sequences encoding TALL-1 (including recombinant nucleicacid molecules), to homologues of such nucleic acid sequences, to TALL-1proteins and fusion proteins and homologues thereof, to polyclonal andmonoclonal antibodies that specifically bind to TALL-1 and/or homologuesor mimetics thereof, and to methods of using such nucleic acidmolecules, proteins and antibodies. The present invention also includesreceptors that are bound by TALL-1, referred to herein as TALL-1receptors. Also included in the present invention are homologues andmimetics of TALL-1 that bind to and regulate (upregulate ordownregulate) the activity of a TALL-1 receptor, as well as TALL-1receptor homologues.

[0050] The present invention also includes methods which use nucleicacid sequences encoding TALL-1, TALL-1 proteins (including TALL-1homologues), TALL-1 antibodies, and TALL-1 receptors (including TALL-1receptor homologues) and TALL-1 receptor antibodies as therapeuticreagents and/or diagnostic tools. As such, one embodiment of the presentinvention relates to a method to identify regulators of TALL-1 byidentifying putative regulatory compounds which increase or decrease theaction (i.e., expression and/or biological activity) of TALL-1 proteinsor nucleic acid molecules and/or TALL-1 receptor proteins or nucleicacid molecules. Another embodiment of the present invention relates to amethod to regulate biological processes, including immune processes,that are mediated by monocytes, macrophages, and/or B lymphocytes.Another embodiment of the present invention relates to a method toidentify regulators of biological processes, including immune processes,that are mediated by monocytes, macrophages, and/or B lymphocytes. Yetanother embodiment of the present invention relates to therapeuticcompositions comprising one or more of TALL-1 proteins, nucleic acidmolecules comprising nucleic acid sequence encoding TALL-1, antibodiesthat specifically bind to TALL-1, inhibitors of TALL-1 proteins, TALL-1receptor proteins, nucleic acid molecules comprising nucleic acidsequence encoding TALL-1 receptor, antibodies that specifically bind toTALL-1 receptor, and/or inhibitors of TALL-1 receptor, that are usefulin a method of regulating biological processes, including immuneprocesses, that are mediated by monocytes, macrophages, and/or Blymphocytes. Yet another embodiment relates to a method to diagnosedisorders related to the biological activity and/or expression (ordisregulation thereof) of TALL-1.

[0051] TALL-1 is a novel TNF family member identified by the presentinventors (Shu et al., (1999), J. Leukocyte Biology 65:680-683) andsubsequently published by three other groups (Schneider et al., (1999),J. Exp. Med. 189:1747-1756; Moore et al., (1999), Science 285:260 -263;Mukhopadhyay et al., (1999), J. Biol. Chem. 274:15978-15981). Unlikemost members of the TNF family which are expressed by activated immunecells, TALL-1 is constitutively expressed by monocytes and macrophages(Shu et al., (1999), J. Leukocyte Biology 65:680-683; Schneider et al.,(1999), J. Exp. Med. 189:1747-1756). Flow cytometry analysis indicatesthat the receptor for TALL-1 is expressed only by peripheral Blymphocytes or B lymphocyte-derived cell lines, but not by peripheral Tlymphocytes, monocytes, and non-B lymphocyte-derived cell lines(Schneider et al., (1999), J. Exp. Med. 189:1747-1756; Moore et al.,(1999), Science 285:260-263). Functional studies indicate that solubleTALL-1 (sTALL-1) co-stimulates B lymphocyte proliferation in vitro andadministration or overexpression of sTALL-1 causes lymphocytic disordersand autoimmune manifestations in mice (Moore et al., (1999), Science285:260-263; Macky et al., (1999), J. Exp. Med. 190:1697-1710). Thesedata suggest that TALL-1 plays an important role inmonocyte/macrophage-driven B lymphocyte activities.

[0052] The present inventors have also identified the receptor forTALL-1 (e.g., the TALL-1 receptor). The present inventors havediscovered that B cell maturation factor, or BCMA, a previouslydescribed member of the TNF receptor family of unknown function which isspecifically expressed by B lymphocytes, is the receptor for TALL-1. Thepresent inventors have additionally discovered that BCMA can activatethe transcription factor NF-κB through a TRAF5, TRAF6, NIK, IKKα andIKKβ dependent pathway. The identification of BCMA as the TALL-1receptor is quite unexpected because, prior to the present invention,investigators studying BCMA reported that the factor was enriched in theGolgi apparatus, but failed to detect BCMA on the plasma membrane (Graset al., (1995), International Immunology 7:1093-1106). In addition,prior sequence analysis suggested that BCMA had no recognizable signalpeptide at its N-terminus (Laabi et al., (1992), EMBO J. 11:3897-3904;Laabi et al., (1994), Nucleic Acids Research 22:1147-1154; Gras et al.,(1995), International Immunology 7:1093-1106) and therefore, it wouldnot be expected to be inserted into the plasma membrane. The discoveryof TALL-1 and of the ligand-receptor relationship between TALL-1 andBCMA (i.e., TALL-1 receptor) as well as the biological activitiesresulting from such a relationship, leads to methods of using bothTALL-1 and BCMA, as well as homologues thereof, which were notpreviously possible or realized.

[0053] Various embodiments of the present invention are described belowinitially with regard to an isolated TALL-1 protein of the presentinvention. It is to be understood, however, that the general definitionsof terms and methods are intended to apply to the discussion of anisolated TALL-1 receptor, also discussed below, unless otherwisemodified within the specific discussion of the TALL-1 receptor.

[0054] Accordingly, one embodiment of the present invention relates toan isolated TALL-1 protein. As used herein, reference to an isolatedprotein, including an isolated TALL-1 protein, includes full-lengthproteins, fusion proteins, or any homologue of such a protein. In oneembodiment, an isolated TALL-1 protein is a membrane protein. In anotherembodiment, an isolated TALL-1 protein is a soluble protein (sTALL-1).An amino acid sequence for soluble TALL-1 spans from amino acidpositions 134 to 285 of SEQ ID NO:2. It is noted that investigators whopublished proteins having the same amino acid sequence as TALL-1subsequent to the filing of the priority application for the presentinvention have given the TALL-1 proteins different names, including: Blymphocyte stimulator (Blys)(Moore et al., July 1999, Science285:260-263), tumor necrosis factor-like protein ZTNF4 (Submitted toGenBank on Sep. 14, 1999, by Biomolecular Informatics, Zymogenetics;released on Jan. 13, 2000), THANK (Mukhopadhyay et al., 1999, J. Biol.Chem. 274:15978-15981), and B-cell activating factor (BAFF) (Schneideret al., June 1999, J. Exp. Med. 189:1747-1756). According to the presentinvention, a homologue of a TALL-1 protein (i.e., a TALL-1 homologue)includes TALL-1 proteins in which at least one or a few, but not limitedto one or a few, amino acids have been deleted (e.g., a truncatedversion of the protein, such as a peptide or fragment), inserted,inverted, substituted and/or derivatized (e.g., by glycosylation,phosphorylation, acetylation, myristoylation, prenylation, palmitation,amidation and/or addition of glycosylphosphatidyl inositol). Preferably,a TALL-1 homologue has TALL-1 biological activity. TALL-1 biologicalactivity is defined herein as at least one of: an ability to bind to aTALL-1 receptor; an ability to costimulate B lymphocyte proliferation;an ability to costimulate B lymphocyte activation; and/or an ability tosupport B lymphocyte survival. In one embodiment, a TALL-1 homologuecomprises a portion of a wild-type TALL-1 protein sufficient to form βstrands. Such portions are illustrated, for example, in FIG. 1B. Inanother embodiment, a TALL-1 homologue comprises at least the amino acidresidues (in the equivalent positions) which are identical in theC-terminal region of several TNF family proteins as illustrated in FIG.1B. Such a homologue also preferably binds specifically to a TALL-1receptor, preferably such that the TALL-1 receptor is activated. It isnoted that reference to a TALL-1 protein is intended to encompassvariants of the TALL-1 sequence, including truncated TALL-1 proteins, inwhich conservative amino acid deletions, additions or substitutions areallowed which do not substantially change the biological activity of theTALL-1 protein with regard to at least one or more of the biologicalactivities of TALL-1 as described above. Using the guidance providedherein, it is within the ability of one of skill in the art to makemodifications in the nucleic acid and/or amino acid sequence ofwild-type TALL-1 (e.g., SEQ ID NOs:1 or 2) and to test homologues havingsuch modifications for one or more biological activities of TALL-1. Forexample, methods for determining binding of TALL-1 to TALL-1 receptorare described in detail in the Examples section and below with regard tothe description of assays for evaluating regulators of the interactionbetween TALL-1 and TALL-1 receptor. In addition, biological andmolecular assays for determining the activation of a TALL-1 receptor asa result of ligation, including B cell proliferation assays, NFκBactivation and activation of other intracellular molecules is describedin the Examples section. More specifically, methods of detecting andmeasuring TALL-1 biological activity include, but are not limited tomeasurement of transcription of TALL-1, measurement of translation ofTALL-1, measurement of secretion of soluble TALL-1 (sTALL-1),measurement of binding of TALL-1 to a TALL-1 receptor, measurement of anincrease in B cell proliferation, measurement of an increase in B cellactivation, measurement of B cell survival. In another embodiment, aTALL-1 homologue may or may not have measurable TALL-1 activity, but isused for the preparation of antibodies or the development ofoligonucleotides useful for identifying other TALL-1 proteins, or foruse in diagnostic assays (described below). In one embodiment of thepresent invention, a TALL-1 homologue that is useful in a method of thepresent invention binds to, but does not activate, a TALL-1 receptor,and therefore serves as a competitive inhibitor of a wild-type TALL-1protein.

[0055] In one embodiment, a TALL-1 protein (e.g., a TALL-1 proteinhomologue) comprises an amino acid sequence that is at least about 40%identical to SEQ ID NO:2 over at least about 175 contiguous amino acidsof SEQ ID NO:2. In another embodiment, a TALL-1 protein comprises anamino acid sequence that is at least about 40% identical to SEQ ID NO:2over positions 134-285 of SEQ ID NO:2. Preferably, a TALL-1 proteincomprises an amino acid sequence that is at least about 50%, and morepreferably, at least about 60%, and more preferably, at least about 70%,and more preferably at least about 80%, and more preferably at leastabout 90%, and even more preferably at least about 95% identical to SEQID NO:2 over at least about 175 amino acids of SEQ ID NO:2, and morepreferably over at least about 200 amino acids, and more preferably overat least about 225 amino acids, and more preferably over at least about250 amino acids, and even more preferably over 275 amino acids of SEQ IDNO:2. In another embodiment, a TALL-1 protein comprises an amino acidsequence that is at least about 50%, and more preferably, at least about60%, and more preferably, at least about 70%, and more preferably atleast about 80%, and more preferably at least about 90%, and even morepreferably at least about 95% identical to SEQ ID NO:2 over positions134-285 of SEQ ID NO:2.

[0056] As used herein, unless otherwise specified, reference to apercent (%) identity refers to an evaluation of homology which isperformed using: (1) a BLAST 2.0 Basic BLAST homology search(http://www.ncbi.nlm.nih.gov/BLAST) using blastp for amino acid searchesand blastn for nucleic acid searches with standard default parameters,wherein the query sequence is filtered for low complexity regions bydefault (described in Altschul, S. F., Madden, T. L., Schääffer, A. A.,Zhang, J., Zhang, Z., Miller, W. & Lipman, D. J. (1997) “Gapped BLASTand PSI-BLAST: a new generation of protein database search programs.”Nucleic Acids Res. 25:3389-3402, incorporated herein by reference in itsentirety); (2) a BLAST 2 alignment (using the parameters describedbelow) (http://www.ncbi.nlm.nih.gov/BLAST); or (3) both BLAST 2.0 andBLAST 2. It is noted that due to some differences in the standardparameters between BLAST 2.0 Basic BLAST and BLAST 2, two specificsequences might be recognized as having significant homology using theBLAST 2 program, whereas a search performed in BLAST 2.0 Basic BLASTusing one of the sequences as the query sequence may not identify thesecond sequence in the top matches. Therefore, it is to be understoodthat percent identity can be determined by using either one or both ofthese programs.

[0057] Two specific sequences can be aligned to one another using BLAST2 sequence as described in Tatusova and Madden, (1999), “Blast 2sequences—a new tool for comparing protein and nucleotide sequences”,FEMS Microbiol Lett. 174:247-250, incorporated herein by reference inits entirety. BLAST 2 sequence alignment is performed in blastp orblastn using the BLAST 2.0 algorithm to perform a Gapped BLAST search(BLAST 2.0) between the two sequences allowing for the introduction ofgaps (deletions and insertions) in the resulting alignment. For purposesof clarity herein, a BLAST 2 sequence alignment is performed using thestandard default parameters as follows. For blastn, using 0 BLOSUM62matrix:

[0058] Reward for match=1

[0059] Penalty for mismatch=−2

[0060] Open gap (5) and extension gap (2) penalties

[0061] gap x_dropoff (50) expect (10) word size (11) filter (on)

[0062] For blastp, using 0 BLOSUM62 matrix:

[0063] Open gap (11) and extension gap (1) penalites

[0064] gap x_dropoff (50) expect (10) word size (3) filter (on).

[0065] In one embodiment of the present invention, a TALL-1 homologue isless than 100% identical to SEQ ID NO:2. In another embodiment, a TALL-1homologue is less than about 95% identical to SEQ ID NO:2, and inanother embodiment, is less than about 90% identical to SEQ ID NO:2, andin another embodiment, is less than about 80% identical to SEQ ID NO:2,and in another embodiment, is less than about 70% identical to SEQ IDNO:2, and in another embodiment, is less than about 60% identical to SEQID NO:2, and in another embodiment, is less than about 50% identical toSEQ ID NO:2.

[0066] A TALL-1 protein can also include proteins having an amino acidsequence comprising at least 30 contiguous amino acid residues of SEQ IDNO:2, (i.e., 30 contiguous amino acid residues having 100% identity with30 contiguous amino acids of SEQ ID NO:2). In a preferred embodiment, ahomologue of a TALL-1 amino acid sequence includes amino acid sequencescomprising at least 50, and more preferably at least 75, and morepreferably at least 100, and more preferably at least 115, and morepreferably at least 130, and more preferably at least 150, and morepreferably at least 200, and even more preferably, at least 250,contiguous amino acid residues of SEQ ID NO:2. A TALL-1 proteinhomologue can include proteins encoded by a nucleic acid sequencecomprising at least 90, and preferably at least 150, and more preferablyat least 225, and more preferably at least 300, and more preferably atleast 345, and more preferably at least 390, and more preferably atleast 450, and more preferably at least 600, and even more preferably atleast 750, contiguous nucleotides of SEQ ID NO:1. In a preferredembodiment, a TALL-1 protein homologue has measurable TALL-1 biologicalactivity (i.e., has biological activity).

[0067] According to the present invention, the term “contiguous” or“consecutive”, with regard to nucleic acid or amino acid sequencesdescribed herein, means to be connected in an unbroken sequence. Forexample, for a first sequence to comprise 30 contiguous (or consecutive)amino acids of a second sequence, means that the first sequence includesan unbroken sequence of 30 amino acid residues that is 100% identical toan unbroken sequence of 30 amino acid residues in the second sequence.Similarly, for a first sequence to have “100% identity” with a secondsequence means that the first sequence exactly matches the secondsequence with no gaps between nucleotides or amino acids.

[0068] In another embodiment, a TALL-1 protein, including a TALL-1protein homologue, includes a protein having an amino acid sequence thatis sufficiently similar to a natural TALL-1 amino acid sequence that anucleic acid sequence encoding the homologue is capable of hybridizingunder low, moderate or high stringency conditions (described below) to(i.e., with) a nucleic acid molecule encoding the natural TALL-1 protein(i.e., to the complement of the nucleic acid strand encoding the naturalTALL-1 amino acid sequence). Preferably, a homologue of a TALL-1 proteinis encoded by a nucleic acid molecule comprising a nucleic acid sequencethat hybridizes under low, moderate, or high stringency conditions tothe complement of a nucleic acid sequence that encodes a proteincomprising an amino acid sequence represented by SEQ ID NO:2. Even morepreferably, a homologue of a TALL-1 protein is encoded by a nucleic acidmolecule comprising a nucleic acid sequence that hybridizes under low,moderate, or high stringency conditions to the complement of SEQ IDNO:1. Such hybridization conditions are described in detail below. Anucleic acid sequence complement of nucleic acid sequence encoding aTALL-1 protein of the present invention refers to the nucleic acidsequence of the nucleic acid strand that is complementary to the strandwhich encodes TALL-1. It will be appreciated that a double stranded DNAwhich encodes a given amino acid sequence comprises a single strand DNAand its complementary strand having a sequence that is a complement tothe single strand DNA. As such, nucleic acid molecules of the presentinvention can be either double-stranded or single-stranded, and includethose nucleic acid molecules that form stable hybrids under stringenthybridization conditions with a nucleic acid sequence that encodes theamino acid sequence SEQ ID NO:2, and/or with the complement of thenucleic acid sequence that encodes an amino acid sequence SEQ ID NO:2.Methods to deduce a complementary sequence are known to those skilled inthe art. It should be noted that since amino acid sequencing and nucleicacid sequencing technologies are not entirely error-free, the sequencespresented herein, at best, represent apparent sequences of a TALL-1protein of the present invention.

[0069] TALL-1 protein homologues can be the result of natural allelicvariation or natural mutation. TALL-1 protein homologues of the presentinvention can also be produced using techniques known in the artincluding, but not limited to, direct modifications to the protein ormodifications to the gene encoding the protein using, for example,classic or recombinant DNA techniques to effect random or targetedmutagenesis. A naturally occurring allelic variant of a nucleic acidencoding TALL-1 is a gene that occurs at essentially the same locus (orloci) in the genome as the gene which encodes an amino acid sequence SEQID NO:2, but which, due to natural variations caused by, for example,mutation or recombination, has a similar but not identical sequence.Natural allelic variants typically encode proteins having similaractivity to that of the protein encoded by the gene to which they arebeing compared. One class of allelic variants can encode the sameprotein but have different nucleic acid sequences due to the degeneracyof the genetic code. Allelic variants can also comprise alterations inthe 5′ or 3′ untranslated regions of the gene (e.g., in regulatorycontrol regions). Allelic variants are well known to those skilled inthe art and would be expected to be found within a given bacterialspecies since the genome is haploid and/or among a group of two or morebacterial species.

[0070] TALL-1 proteins also include expression products of gene fusions(for example, used to overexpress soluble, active forms of therecombinant protein), of mutagenized genes (such as genes having codonmodifications to enhance gene transcription and translation), and oftruncated genes (such as genes having membrane binding domains removedto generate soluble forms of a membrane protein, or genes having signalsequences removed which are poorly tolerated in a particular recombinanthost). It is noted that TALL-1 proteins and protein homologues of thepresent invention include proteins which do not have TALL-1 activity.Such proteins are useful, for example, for the production of antibodiesand for diagnostic assays.

[0071] An isolated TALL-1 protein of the present invention, includingfull-length proteins, truncated proteins, other homologues, and fusionproteins, can be identified in a straight-forward manner: (1) by theprotein's ability to: bind to a TALL-1 receptor; costimulate Blymphocyte proliferation; costimulate B lymphocyte activation; and/orsupport B lymphocyte survival such as is illustrated in the Examples;(2) by the biochemical properties of the protein (e.g., molecularweight, tertiary structure, primary structure); (3) by the protein'sselective binding to an antibody against a TALL-1 protein; and/or (4) byhomology of the protein with other TALL-1 amino acid and nucleic acidsequences such as to TALL-1 amino acid and nucleic acid sequence fromother proteins. The minimum size of a protein and/or homologue of thepresent invention is a size sufficient to have TALL-1 biologicalactivity or, when the protein is not required to have such activity,sufficient to be useful for another purpose associated with a TALL-1protein of the present invention, such as for the production ofantibodies that bind to a naturally occurring TALL-1 protein. As such,the minimum size of a TALL-1 protein or homologue of the presentinvention is a size suitable to form at least one epitope that can berecognized by an antibody, and is typically at least 8 to 30 amino acidsin length, with preferred sizes depending on whether full-length,multivalent (i.e., fusion protein having more than one domain each ofwhich has a function), or functional portions of such proteins aredesired. There is no limit, other than a practical limit, on the maximumsize of such a protein in that the protein can include a portion of aTALL-1 protein (including TALL-1 homologues) or a full-length TALL-1.

[0072] Similarly, the minimum size of a nucleic acid molecule of thepresent invention is a size sufficient to encode a protein having TALL-1biological activity, sufficient to encode a TALL-1 protein comprising atleast one epitope which binds to an antibody, or sufficient to form aprobe or oligonucleotide primer that is capable of forming a stablehybrid with the complementary sequence of a nucleic acid moleculeencoding a natural TALL-1 protein (e.g., under low, moderate or highstringency conditions). As such, the size of the nucleic acid moleculeencoding such a protein can be dependent on nucleic acid composition andpercent homology or identity between the nucleic acid molecule andcomplementary sequence as well as upon hybridization conditions per se(e.g., temperature, salt concentration, and formamide concentration).The minimal size of a nucleic acid molecule that is used as anoligonucleotide primer or as a probe is typically at least about 12 toabout 15 nucleotides in length if the nucleic acid molecules are GC-richand at least about 15 to about 18 bases in length if they are AT-rich.There is no limit, other than a practical limit, on the maximal size ofa nucleic acid molecule of the present invention, in that the nucleicacid molecule can include a portion of a TALL-1 encoding sequence, anucleic acid sequence encoding a full-length TALL-1 protein (including aTALL-1 gene), or multiple genes, or portions thereof.

[0073] The present invention also includes a fusion protein thatincludes a TALL-1-containing domain (including a homologue of a TALL-1protein) attached to one or more fusion segments. Suitable fusionsegments for use with the present invention include, but are not limitedto, segments that can: enhance a protein's stability; provide otherdesirable biological activity (e.g., a cytokine); and/or assist with thepurification of a TALL-1 protein (e.g., by affinity chromatography). Asuitable fusion segment can be a domain of any size that has the desiredfunction (e.g., imparts increased stability, solubility, action orbiological activity; and/or simplifies purification of a protein).Fusion segments can be joined to amino and/or carboxyl termini of theTALL-1-containing domain of the protein and can be susceptible tocleavage in order to enable straight-forward recovery of a TALL-1protein. Fusion proteins are preferably produced by culturing arecombinant cell transfected with a fusion nucleic acid molecule thatencodes a protein including the fusion segment attached to either thecarboxyl and/or amino terminal end of a TALL-1-containing domain.

[0074] The present invention also includes a mimetic of a TALL-1protein. As used herein, the term “mimetic” is used to refer to anypeptide or non-peptide compound that is able to mimic the biologicalaction of a naturally occurring peptide, often because the mimetic has abasic structure that mimics the basic structure of the naturallyoccurring peptide and/or has the salient biological properties of thenaturally occurring peptide. Mimetics can include, but are not limitedto: peptides that have substantial modifications from the prototype suchas no side chain similarity with the naturally occurring peptide (suchmodifications, for example, may decrease its susceptibility todegradation); anti-idiotypic and/or catalytic antibodies, or fragmentsthereof; non-proteinaceous portions of an isolated protein (e.g.,carbohydrate structures); or synthetic or natural organic molecules,including nucleic acids and drugs identified through combinatorialchemistry, for example.

[0075] Such mimetics can be designed, selected and/or otherwiseidentified using a variety of methods known in the art. Various methodsof drug design, useful to design mimetics or other therapeutic compoundsuseful in the present invention are disclosed in Maulik et al., 1997,Molecular Biotechnology: Therapeutic Applications and Strategies,Wiley-Liss, Inc., which is incorporated herein by reference in itsentirety. A TALL-1 mimetic can be obtained, for example, from moleculardiversity strategies (a combination of related strategies allowing therapid construction of large, chemically diverse molecule libraries),libraries of natural or synthetic compounds, in particular from chemicalor combinatorial libraries (i.e., libraries of compounds that differ insequence or size but that have the similar building blocks) or byrational, directed or random drug design. See for example, Maulik etal., supra.

[0076] In a molecular diversity strategy, large compound libraries aresynthesized, for example, from peptides, oligonucleotides, carbohydratesand/or synthetic organic molecules, using biological, enzymatic and/orchemical approaches. The critical parameters in developing a moleculardiversity strategy include subunit diversity, molecular size, andlibrary diversity. The general goal of screening such libraries is toutilize sequential application of combinatorial selection to obtainhigh-affinity ligands for a desired target, and then to optimize thelead molecules by either random or directed design strategies. Methodsof molecular diversity are described in detail in Maulik, et al., ibid.

[0077] Maulik et al. also disclose, for example, methods of directeddesign, in which the user directs the process of creating novelmolecules from a fragment library of appropriately selected fragments;random design, in which the user uses a genetic or other algorithm torandomly mutate fragments and their combinations while simultaneouslyapplying a selection criterion to evaluate the fitness of candidateligands; and a grid-based approach in which the user calculates theinteraction energy between three dimensional receptor structures andsmall fragment probes, followed by linking together of favorable probesites.

[0078] According to the present invention, TALL-1 proteins can bederived from any animal, and particularly, from any animal in theVertebrate class, Mammalia. Preferred TALL-1 proteins include isolatedTALL-1 proteins from human, mouse, rat, cow, pig, baboon, and otherprimates. A particularly preferred isolated TALL-1 protein is a humanTALL-1 protein. TALL-1 proteins from different mammalian organisms sharesignificant homology with each other. For example, the amino acidsequence for murine TALL-1 (GenBank Accession No. AAD22475) is 56%identical (using BLAST 2 alignment, OBLOSUM62 matrix, described below)to the amino acid sequence for human TALL-1 (SEQ ID NO:2).

[0079] Further embodiments of the present invention include nucleic acidmolecules that encode a TALL-1 protein. A nucleic acid molecule of thepresent invention includes a nucleic acid molecule comprising a nucleicacid sequence encoding any of the isolated TALL-1 proteins, including aTALL-1 homologue, described above. A preferred Tall-1 nucleic acidmolecule of the present invention includes a nucleic acid moleculecomprising a nucleic acid sequence encoding a protein having an aminoacid sequence comprising at least 50 contiguous amino acid residues ofSEQ ID NO:2, and preferably at least 75, and more preferably at least100, and more preferably at least 115, and more preferably at least 130,and preferably at least 150, and more preferably at least 175, and morepreferably at least 200, and more preferably at least 225, and even morepreferably at least 250, contiguous amino acid residues of SEQ ID NO:2.In another embodiment, a preferred Tall-i nucleic acid moleculecomprises a nucleic acid sequence comprising at least 150, andpreferably at least 225, and more preferably at least 300, and morepreferably at least 345, and more preferably at least 390, and morepreferably at least 450, and more preferably at least 525, and morepreferably at least 600, and more preferably at least 675, and even morepreferably at least 750, contiguous nucleotides of SEQ ID NO:1.

[0080] In one embodiment, such nucleic acid molecules include isolatednucleic acid molecules that hybridize under low stringency conditions,and more preferably under moderate stringency conditions, and even morepreferably under high stringency conditions, and even more preferablyunder very high stringency conditions with the complement of a nucleicacid sequence encoding a naturally occurring TALL-1 (i.e., includingnaturally occurring allelic variants encoding a TALL-1). Preferably, anisolated nucleic acid molecule encoding a TALL-1 protein of the presentinvention comprises a nucleic acid sequence that hybridizes under low,moderate, or high stringency conditions to the complement of a nucleicacid sequence that encodes a protein comprising an amino acid sequencerepresented by SEQ ID NO:2. In one embodiment, an isolated nucleic acidmolecule comprises a nucleic acid sequence that hybridizes under low,moderate, high or very high stringency conditions to the complement of anucleic acid sequence represented by SEQ ID NO:1

[0081] As used herein, hybridization conditions refer to standardhybridization conditions under which nucleic acid molecules are used toidentify similar nucleic acid molecules. Such standard conditions aredisclosed, for example, in Sambrook et al., Molecular Cloning: ALaboratory Manual, Cold Spring Harbor Labs Press, 1989. Sambrook et al.,ibid., is incorporated by reference herein in its entirety (seespecifically, pages 9.31-9.62). In addition, formulae to calculate theappropriate hybridization and wash conditions to achieve hybridizationpermitting varying degrees of mismatch of nucleotides are disclosed, forexample, in Meinkoth et al., 1984, Anal. Biochem. 138, 267-284; Meinkothet al., ibid., is incorporated by reference herein in its entirety.

[0082] More particularly, low stringency hybridization and washingconditions, as referred to herein, refer to conditions which permitisolation of nucleic acid molecules having at least about 40% nucleicacid sequence identity with the nucleic acid molecule being used toprobe in the hybridization reaction (i.e., conditions permitting about60% or less mismatch of nucleotides). Moderate stringency hybridizationand washing conditions, as referred to herein, refer to conditions whichpermit isolation of nucleic acid molecules having at least about 60%nucleic acid sequence identity with the nucleic acid molecule being usedto probe in the hybridization reaction (i.e., conditions permittingabout 40% or less mismatch of nucleotides). High stringencyhybridization and washing conditions, as referred to herein, refer toconditions which permit isolation of nucleic acid molecules having atleast about 75% nucleic acid sequence identity with the nucleic acidmolecule being used to probe in the hybridization reaction (i.e.,conditions permitting about 20% or less mismatch of nucleotides). Veryhigh stringency hybridization and washing conditions, as referred toherein, refer to conditions which permit isolation of nucleic acidmolecules having at least about 90% nucleic acid sequence identity withthe nucleic acid molecule being used to probe in the hybridizationreaction (i.e., conditions permitting about 10% or less mismatch ofnucleotides). As discussed above, one of skill in the art can use theformulae in Meinkoth et al., ibid. to calculate the appropriatehybridization and wash conditions to achieve these particular levels ofnucleotide mismatch. Such conditions will vary, depending on whetherDNA:RNA or DNA:DNA hybrids are being formed. Calculated meltingtemperatures for DNA:DNA hybrids are 10° C. less than for DNA:RNAhybrids. In particular embodiments, stringent hybridization conditionsfor DNA:DNA hybrids include hybridization at an ionic strength of 6×SSC(0.9 M Na⁺) at a temperature of between about 20° C. and about 35° C.,more preferably, between about 28° C. and about 40° C., and even morepreferably, between about 35° C. and about 45° C. In particularembodiments, stringent hybridization conditions for DNA:RNA hybridsinclude hybridization at an ionic strength of 6×SSC (0.9 M Na⁺) at atemperature of between about 30° C. and about 45° C., more preferably,between about 38° C. and about 50° C., and even more preferably, betweenabout 45° C. and about 55° C. These values are based on calculations ofa melting temperature for molecules larger than about 100 nucleotides,0% formamide and a G+C content of about 40%. Alternatively, Tm can becalculated empirically as set forth in Sambrook et al., supra, pages9.31 to 9.62.

[0083] In one embodiment of the present invention, a nucleic acidmolecule encoding a TALL-1 protein of the present invention comprises anucleic acid sequence that encodes an amino acid sequence that is atleast about 40% identical to SEQ ID NO:2 over at least 175 amino acidsof SEQ ID NO:2. In another embodiment, a nucleic acid molecule encodinga TALL-1 protein of the present invention comprises a nucleic acidsequence that encodes an amino acid sequence that is at least about 40%identical to SEQ ID NO:2 over positions 134-285 of SEQ ID NO:2. In thisembodiment, the nucleic acid molecule is preferably a part of arecombinant nucleic acid molecule. Such a recombinant nucleic acidmolecule comprises an expression vector operatively linked to thenucleic acid molecule. Recombinant nucleic acid molecules are describedin detail below. In this embodiment, the TALL-1 protein preferably hasTALL-1 biological activity. In this embodiment, a nucleic acid moleculeencoding a TALL-1 protein of the present invention more preferablycomprises a nucleic acid sequence that encodes an amino acid sequencethat is at least about 50%, and more preferably, at least about 60%, andmore preferably at least about 70%, and more preferably at least about80%, and more preferably at least about 90%, and even more preferably atleast about 95% identical to SEQ ID NO:2 over at least about 175 aminoacids of SEQ ID NO:2, and more preferably over at least about 200 aminoacids, and more preferably over at least about 225 amino acids, and morepreferably over at least about 250 amino acids, and even more preferablyover 275 amino acids and even more preferably over the full length ofSEQ ID NO:2. In another embodiment, a nucleic acid molecule encoding aTALL-1 protein of the present invention comprises a nucleic acidsequence that encodes an amino acid sequence that is at least about 50%,and more preferably, at least about 60%, and more preferably at leastabout 70%, and more preferably at least about 80%, and more preferablyat least about 90%, and even more preferably at least about 95%identical to positions 134-285 of SEQ ID NO:2. Such a nucleic acidsequence can include a nucleic acid sequence encoding a TALL-1 proteinhomologue, and can therefore be referred to as a homologue of a nucleicacid sequence encoding a naturally occurring TALL-1 (i.e., a nucleicacid sequence homologue).

[0084] In another embodiment, preferred TALL-1 nucleic acid molecules ofthe present invention include nucleic acid molecules which comprise anucleic acid sequence having at least about 40%, and more preferably atleast about 45%, and more preferably at least about 55%, and morepreferably, at least about 65%, and more preferably, at least about 75%,and even more preferably, at least about 85%, and most preferably, atleast about 95% identity with a nucleic acid sequence represented by SEQID NO:1. Preferred TALL-1 nucleic acid molecules of the presentinvention also include: nucleic acid molecules which comprise a nucleicacid sequence encoding a protein comprising an amino acid sequencerepresented by SEQ ID NO:2 or positions 134-285 of SEQ ID NO:2; or anucleic acid molecule comprising a nucleic acid sequence represented bySEQ ID NO:1 or positions 402-855 of SEQ ID NO:1. Percent identity isdetermined using BLAST 2.0 Basic BLAST default parameters, as describedabove.

[0085] In accordance with the present invention, an isolated nucleicacid molecule is a nucleic acid molecule that has been removed from itsnatural milieu (i.e., that has been subject to human manipulation) andcan include DNA, RNA, or derivatives of either DNA or RNA, includingcDNA. As such, “isolated” does not reflect the extent to which thenucleic acid molecule has been purified. An isolated Tall-1 nucleic acidmolecule of the present invention can be isolated from its naturalsource or produced using recombinant DNA technology (e.g., polymerasechain reaction (PCR) amplification, cloning) or chemical synthesis.Isolated Tall-1 nucleic acid molecules can include, for example, Tall-1genes, natural allelic variants of Tall-1 genes, Tall-1 coding regionsor portions thereof, and Tall-1 coding and/or regulatory regionsmodified by nucleotide insertions, deletions, substitutions, and/orinversions in a manner such that the modifications do not substantiallyinterfere with the nucleic acid molecule's ability to encode a TALL-1protein of the present invention or to form stable hybrids understringent conditions with natural gene isolates. An isolated Tall-1nucleic acid molecule can include degeneracies. As used herein,nucleotide degeneracies refers to the phenomenon that one amino acid canbe encoded by different nucleotide codons. Thus, the nucleic acidsequence of a nucleic acid molecule that encodes a TALL-1 protein of thepresent invention can vary due to degeneracies. It is noted that anisolated Tall-1 nucleic acid molecule of the present invention is notrequired to encode a protein having TALL-1 activity. A Tall-1 nucleicacid molecule can encode a truncated, mutated or inactive protein, forexample. Such nucleic acid molecules and the proteins encoded by suchnucleic acid molecules are useful in diagnostic assays, for example, orfor other purposes such as antibody production. As discussed below,antibodies against TALL-1 are useful in a composition and method of thepresent invention.

[0086] According to the present invention, reference to a Tall-1 geneincludes all nucleic acid sequences related to a natural (i.e.wild-type) Tall-1 gene, such as regulatory regions that controlproduction of the TALL-1 protein encoded by that gene (such as, but notlimited to, transcription, translation or post-translation controlregions) as well as the coding region itself. In another embodiment, anTall-1 gene can be a naturally occurring allelic variant that includes asimilar but not identical sequence to the nucleic acid sequence encodinga given TALL-1 protein. Allelic variants have been previously describedabove. The phrases “nucleic acid molecule” and “gene” can be usedinterchangeably when the nucleic acid molecule comprises a gene asdescribed above.

[0087] A Tall-1 nucleic acid molecule homologue (i.e., encoding a TALL-1protein homologue) can be produced using a number of methods known tothose skilled in the art (see, for example, Sambrook et al.). Forexample, nucleic acid molecules can be modified using a variety oftechniques including, but not limited to, by classic mutagenesis andrecombinant DNA techniques (e.g., site-directed mutagenesis, chemicaltreatment, restriction enzyme cleavage, ligation of nucleic acidfragments and/or PCR amplification), or synthesis of oligonucleotidemixtures and ligation of mixture groups to “build” a mixture of nucleicacid molecules and combinations thereof. Another method for modifying arecombinant nucleic acid molecule encoding a TALL-1 protein is geneshuffling (i.e., molecular breeding) (See, for example, U.S. Pat. No.5,605,793 to Stemmer; Minshull and Stemmer; 1999, Curr. Opin. Chem.Biol. 3:284-290; Stemmer, 1994, P.N.A.S. USA 91:10747-10751, all ofwhich are incorporated herein by reference in their entirety). Thistechnique can be used to efficiently introduce multiple simultaneouspositive changes in the TALL-1 protein action. Nucleic acid moleculehomologues can be selected by hybridization with a Tall-1 gene or byscreening the function of a protein encoded by a nucleic acid molecule(e.g., ability to increase B cell proliferation).

[0088] One embodiment of the present invention includes a recombinantnucleic acid molecule, which includes at least one isolated nucleic acidmolecule of the present invention inserted into any nucleic acid vector(e.g., a recombinant vector) which is suitable for cloning, sequencing,and/or otherwise manipulating the nucleic acid molecule, such asexpressing and/or delivering the nucleic acid molecule into a host cellto form a recombinant cell. Such a vector contains heterologous nucleicacid sequences, that is nucleic acid sequences that are not naturallyfound adjacent to nucleic acid molecules of the present invention,although the vector can also contain regulatory nucleic acid sequences(e.g., promoters, untranslated regions) which are naturally foundadjacent to nucleic acid molecules of the present invention (discussedin detail below). The vector can be either RNA or DNA, eitherprokaryotic or eukaryotic, and typically is a virus or a plasmid. Thevector can be maintained as an extrachromosomal element (e.g., aplasmid) or it can be integrated into the chromosome. The entire vectorcan remain in place within a host cell, or under certain conditions, theplasmid DNA can be deleted, leaving behind the nucleic acid molecule ofthe present invention. The integrated nucleic acid molecule can be underchromosomal promoter control, under native or plasmid promoter control,or under a combination of several promoter controls. Single or multiplecopies of the nucleic acid molecule can be integrated into thechromosome.

[0089] Typically, a recombinant molecule includes a nucleic acidmolecule of the present invention operatively linked to one or moretranscription control sequences. As used herein, the phrase “recombinantmolecule” or “recombinant nucleic acid molecule” primarily refers to anucleic acid molecule or nucleic acid sequence operatively linked to atranscription control sequence, but can be used interchangeably with thephrase “nucleic acid molecule”, when such nucleic acid molecule is arecombinant molecule as discussed herein. According to the presentinvention, the phrase “operatively linked” refers to linking a nucleicacid molecule to a transcription control sequence in a manner such thatthe molecule is able to be expressed when transfected (i.e.,transformed, transduced, transfected, conjugated or conduced) into ahost cell. Transcription control sequences are sequences which controlthe initiation, elongation, or termination of transcription.Particularly important transcription control sequences are those whichcontrol transcription initiation, such as promoter, enhancer, operatorand repressor sequences. Suitable transcription control sequencesinclude any transcription control sequence that can function in at leastone of the recombinant cells useful for expressing a TALL-1 protein ofthe present invention. A variety of such transcription control sequencesare known to those skilled in the art. Preferred transcription controlsequences include those which function in bacterial, fungal (e.g.,yeast), insect, plant or animal cells, and particularly, in mammaliancells including, but not limited to, monocytes or macrophages.

[0090] Recombinant molecules of the present invention, which can beeither DNA or RNA, can also contain additional regulatory sequences,such as translation regulatory sequences, origins of replication, andother regulatory sequences that are compatible with the recombinantcell. In one embodiment, a recombinant molecule of the presentinvention, including those which are integrated into the host cellchromosome, also contains secretory signals (i.e., signal segmentnucleic acid sequences) to enable an expressed TALL-1 protein to besecreted from the cell that produces the protein. Suitable signalsegments include a signal segment that is naturally associated with aTALL-1 protein of the present invention or any heterologous signalsegment capable of directing the secretion of a TALL-1 protein accordingto the present invention. In another embodiment, a recombinant moleculeof the present invention comprises a leader sequence to enable anexpressed TALL-1 protein to be delivered to and inserted into themembrane of a host cell. Suitable leader sequences include a leadersequence that is naturally associated with a TALL-1 protein of thepresent invention, or any heterologous leader sequence capable ofdirecting the delivery and insertion of a TALL-1 protein to the membraneof a cell.

[0091] One type of recombinant molecule, referred to herein as arecombinant virus, includes a recombinant nucleic acid molecule of thepresent invention that is packaged in a viral coat and that can beexpressed in a cell after delivery of the virus to the cell. A number ofrecombinant virus particles can be used, including, but not limited to,those based on alphaviruses, baculoviruses, poxviruses, adenoviruses,herpesviruses, and retroviruses.

[0092] One or more recombinant molecules of the present invention can beused to produce an encoded product (e.g., a TALL-1 protein) of thepresent invention. In one embodiment, an encoded product is produced byexpressing a nucleic acid molecule as described herein under conditionseffective to produce the protein. A preferred method to produce anencoded protein is by transfecting a host cell with one or morerecombinant molecules to form a recombinant cell. Suitable host cells totransfect include, but are not limited to, any bacterial, fungal (e.g.,yeast), insect, plant or animal cell that can be transfected. Host cellscan be either untransfected cells or cells that are already transfectedwith at least one nucleic acid molecule. Preferred host cells for use inthe present invention include any microorganism cell which is suitablefor expression of a TALL-1 protein of the present invention, including,but not limited to, bacterial cells including, but not limited toEscherichia coli, and macrophages or monocytes from any species ofanimal.

[0093] According to the present invention, the term “transfection” isused to refer to any method by which an exogenous nucleic acid molecule(i.e., a recombinant nucleic acid molecule) can be inserted into thecell. The term “transformation” can be used interchangeably with theterm “transfection” when such term is used to refer to the introductionof nucleic acid molecules into microbial cells, such as bacteria andyeast. In microbial systems, the term “transformation” is used todescribe an inherited change due to the acquisition of exogenous nucleicacids by the microorganism and is essentially synonymous with the term“transfection”. However, in animal cells, transformation has acquired asecond meaning which can refer to changes in the growth properties ofcells in culture after they become cancerous, for example. Therefore, toavoid confusion, the term “transfection” is preferably used with regardto the introduction of exogenous nucleic acids into animal cells, andthe term “transfection” will be used herein to generally encompass bothtransfection of animal cells and transformation of microbial cells, tothe extent that the terms pertain to the introduction of exogenousnucleic acids into a cell. Therefore, transfection techniques include,but are not limited to, transformation, electroporation, microinjection,lipofection, adsorption, infection and protoplast fusion.

[0094] In one embodiment, an isolated TALL-1 protein of the presentinvention is produced by culturing a cell that expresses the proteinunder conditions effective to produce the protein, and recovering theprotein. A preferred cell to culture is a recombinant cell of thepresent invention. Effective culture conditions include, but are notlimited to, effective media, bioreactor, temperature, pH and oxygenconditions that permit protein production. An effective medium refers toany medium in which a cell is cultured to produce a TALL-1 protein ofthe present invention. Such medium typically comprises an aqueous mediumhaving assimilable carbon, nitrogen and phosphate sources, andappropriate salts, minerals, metals and other nutrients, such asvitamins. Examples of suitable media and culture conditions arediscussed in detail in the Examples section. Cells of the presentinvention can be cultured in conventional fermentation bioreactors,shake flasks, test tubes, microtiter dishes, and petri plates. Culturingcan be carried out at a temperature, pH and oxygen content appropriatefor a recombinant cell. Such culturing conditions are within theexpertise of one of ordinary skill in the art.

[0095] Depending on the vector and host system used for production,resultant proteins of the present invention may either remain within therecombinant cell; be secreted into the culture medium; be secreted intoa space between two cellular membranes, such as the periplasmic space inE. coli; or be retained on the outer surface of a cell or viralmembrane. The phrase “recovering the protein” refers to collecting thewhole culture medium containing the protein and need not implyadditional steps of separation or purification. Proteins of the presentinvention can be purified using a variety of standard proteinpurification techniques, such as, but not limited to, affinitychromatography, ion exchange chromatography, filtration,electrophoresis, hydrophobic interaction chromatography, gel filtrationchromatography, reverse phase chromatography, concanavalin Achromatography, chromatofocusing and differential solubilization.Proteins of the present invention are preferably retrieved in“substantially pure” form. As used herein, “substantially pure” refersto a purity that allows for the effective use of the protein as abiocatalyst or other reagent.

[0096] The present invention also includes isolated (i.e., removed fromtheir natural milieu) antibodies capable of selectively binding to aTALL-1 protein of the present invention or a mimetic thereof (e.g.,TALL-1 antibodies). As used herein, the term “selectively binds to”refers to the ability of antibodies of the present invention topreferentially bind to specified proteins and mimetics thereof of thepresent invention. Binding can be measured using a variety of methodsstandard in the art including enzyme immunoassays (e.g., ELISA),immunoblot assays, etc.; see, for example, Sambrook et al., ibid. In oneembodiment, a TALL-1 antibody preferably selectively binds to a TALL-1protein in such a way as to reduce the activity of that protein, such asby blocking the ability of the protein to bind to its receptor (i.e., aTALL-1 receptor). Isolated antibodies of the present invention caninclude serum containing such antibodies, or antibodies that have beenpurified to varying degrees. Antibodies of the present invention can bepolyclonal or monoclonal, functional equivalents such as antibodyfragments and genetically-engineered antibodies, including single chainantibodies or chimeric antibodies, including bi-specific antibodies thatcan bind to more than one epitope. A TALL-1 antibody is described in theExamples section (see Example 1).

[0097] A preferred method to produce antibodies of the present inventionincludes (a) administering to an animal an effective amount of aprotein, peptide or mimetic thereof of the present invention to producethe antibodies and (b) recovering the antibodies. In another method,antibodies of the present invention are produced recombinantly usingtechniques as heretofore disclosed to produce TALL-1 proteins of thepresent invention. Antibodies raised against defined proteins ormimetics can be advantageous because such antibodies are notsubstantially contaminated with antibodies against other substances thatmight otherwise cause interference in a diagnostic assay or side effectsif used in a therapeutic composition.

[0098] As discussed above, the present inventors have discovered thatthe receptor for TALL-1 is a protein called B cell maturation factor(BCMA, primarily referred to herein as the TALL-1 receptor). A nucleicacid molecule encoding human BCMA (TALL-1 receptor) is identified asGenBank Accession No. U95742, and the human BCMA (TALL-1 receptor)protein is identified under GenBank Accession No. AAB67251 or SwissProtAccession No. Q02223. A nucleic acid molecule comprising a nucleic acidsequence encoding human BCMA (TALL-1 receptor) is also representedherein as SEQ ID NO:10, with the coding region spanning from nucleotidepositions 67-621 of SEQ ID NO:10. SEQ ID NO:10 encodes a 184 amino acidBCMA (TALL-1 receptor) protein represented herein as SEQ ID NO:11. Anucleic acid molecule encoding murine BCMA (TALL-1 receptor) isidentified as GenBank Accession No. AF061505, and the murine BCMA(TALL-1 receptor) protein is identified under GenBank Accession No.AAC23799. A nucleic acid molecule comprising a nucleic acid sequenceencoding murine BCMA (TALL-1 receptor) is also represented herein as SEQID NO:16. SEQ ID NO:16 encodes a 185 amino acid BCMA (TALL-1 receptor)protein represented herein as SEQ ID NO:17. According to the presentinvention, reference to a TALL-1 receptor includes full-length TALL-1receptor proteins, fusion proteins, or any homologue of such a protein.

[0099] Knowing the identity of the receptor for TALL-1 allows one ofskill in the art to modify the receptor in a manner that the ability ofthe receptor to interact with TALL-1 and be activated by TALL-1 can beregulated. Therefore, yet another embodiment of the present inventionrelates to an isolated TALL-1 receptor homologue, wherein said homologuecomprises an amino acid sequence that is: (a) at least about 40%identical to SEQ ID NO:11 over at least 35 amino acids of SEQ ID NO:11;and, (b) less than 100% identical to an amino acid sequence selectedfrom the group of SEQ ID NO:11 and SEQ ID NO:17. According to thepresent invention, a homologue of a TALL-1 receptor (i.e., a TALL-1receptor homologue) includes TALL-1 receptors in which at least one or afew, but not limited to one or a few, amino acids have been deleted(e.g., a truncated version of the protein, such as a peptide orfragment), inserted, inverted, substituted and/or derivatized (e.g., byglycosylation, phosphorylation, acetylation, myristoylation,prenylation, palmitation, amidation and/or addition ofglycosylphosphatidyl inositol).

[0100] Preferably, an isolated TALL-1 receptor homologue of the presentinvention has TALL-1 receptor biological activity. TALL-1 biologicalactivity can include, but is not limited to: TALL-1 receptortranscription, TALL-1 receptor translation, TALL-1 receptorphosphorylation, binding to TALL-1, receptor translocation within acell, NFκB activation, TRAF5, TRAF6, NIK, IKKα and/or IKKβ activation,costimulation of B cell proliferation, costimulation of B cellactivation, and enhancement of B cell survival. Such activities andmethods of detecting the same are described in the Examples sectionand/or are known in the art, given the guidance provided herein.

[0101] Preferably, an isolated TALL-1 receptor homologue of the presentinvention is at least about 45% identical to SEQ ID NO:11 over at least35 amino acids of SEQ ID NO:11, and more preferably at least about 50%identical, and more preferably at least about 55% identical, and morepreferably at least about 60% identical, and even more preferably atleast about 65% identical, and even more preferably at least about 70%identical, and even more preferably at least about 75% identical andeven more preferably at least about 80% identical, and even morepreferably at least about 85% identical, and even more preferably atleast about 90% identical to SEQ ID NO:11 over at least about 35 aminoacids, and more preferably at least 50 amino acids, and more preferablyat least 75 amino acids and more preferably at least 100 amino acids,and more preferably at least 125 amino acids, and more preferably atleast 150 amino acids, and even more preferably at least 175 aminoacids, and even more preferably, over the full-length of SEQ ID NO:11.

[0102] As discussed above, a TALL-1 receptor homologue is less than 100%identical to SEQ ID NO:11 and SEQ ID NO:17. In one embodiment, a TALL-1receptor homologue is less than about 95% identical to SEQ ID NO:11 andSEQ ID NO:17, and in another embodiment, is less than about 90%identical to SEQ ID NO:11 and SEQ ID NO:17, and in another embodiment,is less than about 80% identical to SEQ ID NO:11 and SEQ ID NO:17, andin another embodiment, is less than about 70% identical to SEQ ID NO:11and SEQ ID NO:17, and in another embodiment, is less than about 60%identical to SEQ ID NO:11 and SEQ ID NO:17, and in another embodiment,is less than about 50% identical to SEQ ID NO:11 and SEQ ID NO:17.

[0103] In one embodiment, such a TALL-1 receptor homologue is encoded bya nucleic acid molecule comprising a nucleic acid sequence thathybridizes under moderate stringency conditions to the complement of SEQID NO:10. In another embodiment, such a TALL-1 receptor homologue isencoded by a nucleic acid molecule comprising a nucleic acid sequencethat hybridizes under high stringency conditions to the complement ofSEQ ID NO:10. Hybridization conditions have been discussed in detailwith regard to the TALL-1 protein above and are the same with regard toa TALL-1 receptor homologue.

[0104] In one embodiment, a TALL-1 receptor homologue is a solubleTALL-1 receptor, such as the soluble TALL-1 receptor described in theExamples section. In another embodiment, a TALL-1 receptor homologuebinds to TALL-1, and in one aspect of this embodiment, such a TALL-1receptor homologue is not activated by the binding of TALL-1 as would bea wild-type TALL-1 receptor. In another embodiment, a TALL-1 receptorhomologue does not bind to TALL-1, or binds with less affinity to TALL-1as compared to the wild-type receptor. In yet another embodiment, theTALL-1 receptor homologue activates NF-κB in a cell expressing thehomologue (e.g., a B lymphocyte) through a TRAF5, TRAF6, NIK, IKKα andIKKβ dependent pathway. In another embodiment, the TALL-1 receptorhomologue costimulates B lymphocyte proliferation in a B lymphocyteexpressing the homologue.

[0105] The present invention also includes a fusion protein thatincludes a TALL-1 receptor-containing domain (including a homologue of aTALL-1 receptor) attached to one or more fusion segments. Suitablefusion segments for use with the present invention include, but are notlimited to, segments that can: enhance a protein's stability; provideother desirable biological activity (e.g., a cytokine); and/or assistwith the purification of a TALL-1 receptor (e.g., by affinitychromatography). A suitable fusion segment can be a domain of any sizethat has the desired function (e.g., imparts increased stability,solubility, action or biological activity; and/or simplifiespurification of a protein). Fusion segments can be joined to aminoand/or carboxyl termini of the TALL-1 receptor-containing domain of theprotein and can be susceptible to cleavage in order to enablestraight-forward recovery of a TALL-1 receptor. Fusion proteins arepreferably produced by culturing a recombinant cell transfected with afusion nucleic acid molecule that encodes a protein including the fusionsegment attached to either the carboxyl and/or amino terminal end of aTALL-1 receptor-containing domain.

[0106] The present invention also includes a mimetic of a TALL-1receptor. The term “mimetic” has been defined above. TALL-1 receptormimetics can include, but are not limited to: peptides that havesubstantial modifications from the prototype such as no side chainsimilarity with the naturally occurring peptide (such modifications, forexample, may decrease its susceptibility to degradation); anti-idiotypicand/or catalytic antibodies, or fragments thereof; non-proteinaceousportions of an isolated protein (e.g., carbohydrate structures); orsynthetic or natural organic molecules, including nucleic acids anddrugs identified through combinatorial chemistry, for example.

[0107] Yet another embodiment of the present invention relates to anisolated nucleic acid molecule comprising a nucleic acid sequenceencoding any of the above-identified TALL-1 receptor homologues. In oneembodiment, the nucleic acid sequence encodes a homologue comprising anamino acid sequence that is: (a) at least about 40% identical to SEQ IDNO:11 over at least 35 amino acids of SEQ ID NO:11; and/or, (b) lessthan 100% identical to an amino acid sequence selected from the groupconsisting of SEQ ID NO:11 and SEQ ID NO:17. Also included in thepresent invention are recombinant nucleic acid molecules, recombinantviruses and recombinant cells comprising such a nucleic acid molecule.Recombinant nucleic acid molecules, viruses, and cells have beendescribed in detail above with regard to TALL-1 proteins and thatdiscussion is applied here to recombinant nucleic acid molecules,viruses and cells comprising nucleic acid molecules encoding TALL-1receptor homologues.

[0108] Also included in the present invention is a method to produce aTALL-1 receptor homologue, comprising expressing a nucleic acid moleculeas described herein under conditions effective to produce the homologue.A preferred method to produce an encoded protein is by transfecting ahost cell with one or more recombinant molecules to form a recombinantcell. Suitable host cells to transfect include, but are not limited to,any bacterial, fungal (e.g., yeast), insect, plant or animal cell thatcan be transfected. Host cells can be either untransfected cells orcells that are already transfected with at least one nucleic acidmolecule. Preferred host cells for use in the present invention includeany microorganism cell which is suitable for expression of a TALL-1receptor protein of the present invention, including, but not limitedto, bacterial cells including, but not limited to Escherichia coli, andB lymphocytes from any species of animal.

[0109] Yet another embodiment of the present invention relates to anisolated antibody that selectively binds to a TALL-1 receptor, includinga TALL-1 receptor homologues and mimetics. In one embodiment, a TALL-1receptor antibody preferably selectively binds to a TALL-1 receptor insuch a way as to reduce the activity of that protein, such as byblocking the ability of the receptor to bind to its ligand (i.e., aTALL-1 protein). Isolated antibodies of the present invention caninclude serum containing such antibodies, or antibodies that have beenpurified to varying degrees. Antibodies of the present invention can bepolyclonal or monoclonal, functional equivalents such as antibodyfragments and genetically-engineered antibodies, including single chainantibodies or chimeric antibodies, including bi-specific antibodies thatcan bind to more than one epitope.

[0110] Having described TALL-1 proteins and TALL-1 receptors in detail,various aspects of the present invention related to the use of TALL-1and its receptor will be described. One such embodiment of the presentinvention relates to a composition comprising: (a) a compound selectedfrom the group consisting of: (i) an isolated TALL-1 protein; (ii) anisolated antibody that specifically binds to a TALL-1 protein of (i);(iii) an isolated TALL-1 receptor; and, (iv) an isolated antibody thatspecifically binds to a TALL-1 receptor of (iii); and, (b) apharmaceutically acceptable carrier. In this aspect of the presentinvention, an isolated TALL-1 protein can be any of the TALL-1 proteinspreviously described herein, including, but not limited to, a wild-typeTALL-1 protein, a TALL-1 protein homologue, a soluble TALL-1 protein,and/or a TALL-1 fusion protein. Similarly, an isolated TALL-1 receptorcan be any of the TALL-1 receptor proteins previously described herein,including, but not limited to, a wild-type TALL-1 receptor, a TALL-1receptor homologue, a soluble TALL-1 receptor, and/or a TALL-1 receptorfusion protein. An isolated antibody that selectively binds to a TALL-1protein or a TALL-1 receptor has also been described above. In oneembodiment, a composition of the present invention can include nucleicacid molecules encoding TALL-1 and/or a TALL-1 receptor, and/or amimetic of TALL-1 or a TALL-1 receptor. In one embodiment, a compositionof the present invention includes a combination of at least two of anyof the above-identified compounds.

[0111] Compositions of the present invention are useful for regulatingbiological processes mediated by monocytes, macrophages, B lymphocytes,and/or interactions between B lymphocytes and monocytes or macrophages.In particular, compositions of the present invention are useful forregulating the interaction between TALL-1 and its receptor (TALL-1receptor or BCMA). In some embodiments, such compositions are useful forincreasing (e.g., costimulating, enhancing, upregulating) theinteraction between TALL-1 and its receptor. In this embodiment, thecomposition is used, for example, in a method to activate a TALL-1receptor, or more particularly, to increase B lymphocyte proliferation,to increase B lymphocyte activation, or to increase B lymphocytesurvival. Such methods, described in detail below, are especially usefulto enhance vaccination protocols, to treat patients in which Blymphocyte proliferation, activation or survival is inadequate, or toenhance B lymphocyte proliferation, activation or survival in an invitro assay.

[0112] In some embodiments, such compositions are useful for decreasing(e.g., inhibiting, reducing, downregulating) the interaction betweenTALL-1 and its receptor. In this embodiment, the composition is used,for example, in a method to inhibit activation of a TALL-1 receptor, ormore particularly, to decrease B lymphocyte proliferation, to decrease Blymphocyte activation, or to decrease B lymphocyte survival. Suchmethods, also described in detail below, are especially useful to treatpatients in which inhibition of B lymphocyte proliferation, activationand/or survival is beneficial. Specifically, such methods are useful fortreating patients with an autoimmune disease, and particularly anautoimmune disease in which B lymphocyte proliferation, activation orsurvival is problematic. Such autoimmune diseases include, but are notlimited to, rheumatoid arthritis, systemic lupus erythematosus, insulindependent diabetes mellitis, multiple sclerosis, myasthenia gravis,Grave's disease, autoimmune hemolytic anemia, autoimmunethrombocytopenia purpura, Goodpasture's syndrome, pemphigus vulgaris,acute rheumatic fever, post-streptococcal glomerulonephritis, orpolyarteritis nodosa.

[0113] According to the present invention, a “pharmaceuticallyacceptable carrier” includes pharmaceutically acceptable excipientsand/or pharmaceutically acceptable delivery vehicles, which are suitablefor use in administration of the composition to a suitable in vitro, exvivo or in vivo site. A suitable in vitro, in vivo or ex vivo site ispreferably a monocyte or macrophage, when TALL-1 is the target molecule(i.e., the molecule which is to be regulated or otherwise targeted bythe composition), and a B lymphocyte, when TALL-1 receptor is thetarget. In some embodiments, a suitable site for delivery is a site ofinteraction between B lymphocytes and monocytes or macrophages.Preferred pharmaceutically acceptable carriers are capable ofmaintaining a protein, compound, or recombinant nucleic acid molecule ofthe present invention in a form that, upon arrival of the protein,compound, or recombinant nucleic acid molecule at the cell target in aculture or in patient, the protein, compound or recombinant nucleic acidmolecule is capable of interacting with its target (e.g., a naturallyoccurring TALL-1 protein, including membrane and/or soluble TALL-1proteins, or a TALL-1 receptor).

[0114] Suitable excipients of the present invention include excipientsor formularies that transport or help transport, but do not specificallytarget a composition to a cell (also referred to herein as non-targetingcarriers). Examples of pharmaceutically acceptable excipients include,but are not limited to water, phosphate buffered saline, Ringer'ssolution, dextrose solution, serum-containing solutions, Hank'ssolution, other aqueous physiologically balanced solutions, oils, estersand glycols. Aqueous carriers can contain suitable auxiliary substancesrequired to approximate the physiological conditions of the recipient,for example, by enhancing chemical stability and isotonicity.

[0115] Suitable auxiliary substances include, for example, sodiumacetate, sodium chloride, sodium lactate, potassium chloride, calciumchloride, and other substances used to produce phosphate buffer, Trisbuffer, and bicarbonate buffer. Auxiliary substances can also includepreservatives, such as thimerosal,—or o-cresol, formalin and benzolalcohol. Compositions of the present invention can be sterilized byconventional methods and/or lyophilized.

[0116] One type of pharmaceutically acceptable carrier includes acontrolled release formulation that is capable of slowly releasing acomposition of the present invention into a patient or culture. As usedherein, a controlled release formulation comprises a compound of thepresent invention (e.g., a protein (including homologues), an antibody,a nucleic acid molecule, or a mimetic) in a controlled release vehicle.Suitable controlled release vehicles include, but are not limited to,biocompatible polymers, other polymeric matrices, capsules,microcapsules, microparticles, bolus preparations, osmotic pumps,diffusion devices, liposomes, lipospheres, and transdermal deliverysystems. Other carriers of the present invention include liquids that,upon administration to a patient, form a solid or a gel iii situ.Preferred carriers are also biodegradable (i.e., bioerodible). When thecompound is a recombinant nucleic acid molecule, suitable deliveryvehicles include, but are not limited to liposomes, viral vectors orother delivery vehicles, including ribozymes. Natural lipid-containingdelivery vehicles include cells and cellular membranes. Artificiallipid-containing delivery vehicles include liposomes and micelles. Adelivery vehicle of the present invention can be modified to target to aparticular site in a patient, thereby targeting and making use of acompound of the present invention at that site. Suitable modificationsinclude manipulating the chemical formula of the lipid portion of thedelivery vehicle and/or introducing into the vehicle a targeting agentcapable of specifically targeting a delivery vehicle to a preferredsite, for example, a preferred cell type. Other suitable deliveryvehicles include gold particles, poly-L-lysine/DNA-molecular conjugates,and artificial chromosomes.

[0117] A pharmaceutically acceptable carrier which is capable oftargeting is herein referred to as a “delivery vehicle.” Deliveryvehicles of the present invention are capable of delivering acomposition of the present invention to a target site in a patient. A“target site” refers to a site in a patient to which one desires todeliver a composition. For example, a target site can be any cell whichis targeted by direct injection or delivery using liposomes, viralvectors or other delivery vehicles, including ribozymes. Examples ofdelivery vehicles include, but are not limited to, artificial andnatural lipid-containing delivery vehicles, viral vectors, andribozymes. Natural lipid-containing delivery vehicles include cells andcellular membranes. Artificial lipid-containing delivery vehiclesinclude liposomes and micelles. A delivery vehicle of the presentinvention can be modified to target to a particular site in a mammal,thereby targeting and making use of a compound of the present inventionat that site. Suitable modifications include manipulating the chemicalformula of the lipid portion of the delivery vehicle and/or introducinginto the vehicle a compound capable of specifically targeting a deliveryvehicle to a preferred site, for example, a preferred cell type.Specifically, targeting refers to causing a delivery vehicle to bind toa particular cell by the interaction of the compound in the vehicle to amolecule on the surface of the cell. Suitable targeting compoundsinclude ligands capable of selectively (i.e., specifically) bindinganother molecule at a particular site. Examples of such ligands includeantibodies, antigens, receptors and receptor ligands. Manipulating thechemical formula of the lipid portion of the delivery vehicle canmodulate the extracellular or intracellular targeting of the deliveryvehicle. For example, a chemical can be added to the lipid formula of aliposome that alters the charge of the lipid bilayer of the liposome sothat the liposome fuses with particular cells having particular chargecharacteristics.

[0118] One preferred delivery vehicle of the present invention is aliposome. A liposome is capable of remaining stable in an animal for asufficient amount of time to deliver a nucleic acid molecule describedin the present invention to a preferred site in the animal. A liposome,according to the present invention, comprises a lipid composition thatis capable of delivering a nucleic acid molecule described in thepresent invention to a particular, or selected, site in a patient. Aliposome according to the present invention comprises a lipidcomposition that is capable of fusing with the plasma membrane of thetargeted cell to deliver a nucleic acid molecule into a cell. Suitableliposomes for use with the present invention include any liposome.Preferred liposomes of the present invention include those liposomescommonly used in, for example, gene delivery methods known to those ofskill in the art. More preferred liposomes comprise liposomes having apolycationic lipid composition and/or liposomes having a cholesterolbackbone conjugated to polyethylene glycol. Complexing a liposome with anucleic acid molecule of the present invention can be achieved usingmethods standard in the art.

[0119] Another preferred delivery vehicle comprises a viral vector. Aviral vector includes an isolated nucleic acid molecule useful in thepresent invention, in which the nucleic acid molecules are packaged in aviral coat that allows entrance of DNA into a cell. A number of viralvectors can be used, including, but not limited to, those based onalphaviruses, poxviruses, adenoviruses, herpesviruses, lentiviruses,adeno-associated viruses and retroviruses.

[0120] A composition of the present invention can be delivered to a cellculture or patient by any suitable method. Selection of such a methodwill vary with the type of compound being administered or delivered(i.e., protein, nucleic acid, mimetic), the mode of delivery (i.e., invitro, in vivo, ex vivo) and the goal to be achieved byadministration/delivery of the compound or composition. According to thepresent invention, an effective administration protocol (i.e.,administering a composition in an effective manner) comprises suitabledose parameters and modes of administration that result in delivery of acomposition to a desired site (i.e., to a desired cell) and/or inregulation of B lymphocyte proliferation, B lymphocyte activation and/orB lymphocyte survival in a patient. Administration routes include invivo, in vitro and ex vivo routes. In vivo routes include, but are notlimited to, oral, nasal, intratracheal injection, inhaled, transdermal,rectal, and parenteral routes. Preferred parenteral routes can include,but are not limited to, subcutaneous, intradermal, intravenous,intramuscular and intraperitoneal routes. In a preferred embodiment ofthe present invention, a composition containing a TALL-1 or TALL-1receptor protein, antibody, mimetic, or nucleic acid molecule of thepresent invention is administered by a parenteral route. Intravenous,intraperitoneal, intradermal, subcutaneous and intramuscularadministrations can be performed using methods standard in the art.Aerosol (inhalation) delivery can also be performed using methodsstandard in the art (see, for example, Stribling et al., Proc. Natl.Acad. Sci. USA 189:11277-11281, 1992, which is incorporated herein byreference in its entirety). Oral delivery can be performed by complexinga therapeutic composition of the present invention to a carrier capableof withstanding degradation by digestive enzymes in the gut of ananimal. Examples of such carriers, include plastic capsules or tablets,such as those known in the art. Such routes can include the use ofpharmaceutically acceptable carriers as described above. Ex vivo refersto performing part of the regulatory step outside of the patient, suchas by transfecting a population of cells removed from a patient with arecombinant molecule comprising a nucleic acid sequence encoding aprotein according to the present invention under conditions such thatthe recombinant molecule is subsequently expressed by the transfectedcell, and returning the transfected cells to the patient. In vitro andex vivo routes of administration of a composition to a culture of hostcells can be accomplished by a method including, but not limited to,transfection, transformation, electroporation, microinjection,lipofection, adsorption, protoplast fusion, use of protein carryingagents, use of ion carrying agents, use of detergents for cellpermeabilization, and simply mixing (e.g., combining) a compound inculture with a target cell.

[0121] In accordance with the present invention, a suitable single dosesize is a dose that is capable of regulating B lymphocyte proliferation,activation and/or survival when administered one or more times over asuitable time period. Doses can vary depending upon the goal of theadministration or the condition or the disease being treated.Preferably, a protein or antibody of the present invention isadministered in an amount that is between about 50 U/kg and about 15,000U/kg body weight of the patient. In another embodiment, a protein orantibody is administered in an amount that is between about 0.01 μg andabout 10 mg per kg body weight of the patient, and more preferably,between about 0.1 μg and about 100 μg per kg body weight of the patient.When the compound to be delivered is a nucleic acid molecule, anappropriate single dose results in at least about 1 pg of proteinexpressed per mg of total tissue protein per μg of nucleic aciddelivered. More preferably, an appropriate single dose is a dose whichresults in at least about 10 pg of protein expressed per mg of totaltissue protein per μg of nucleic acid delivered; and even morepreferably, at least about 50 pg of protein expressed per mg of totaltissue protein per μg of nucleic acid delivered; and most preferably, atleast about 100 pg of protein expressed per mg of total tissue proteinper μg of nucleic acid delivered. A preferred single dose of a nakednucleic acid vaccine ranges from about 1 nanogram (ng) to about 100 μg,depending on the route of administration and/or method of delivery, ascan be determined by those skilled in the art. Suitable delivery methodsinclude, for example, by injection, as drops, aerosolized and/ortopically. In one embodiment, pure DNA constructs cover the surface ofgold particles (1 to 3 μm in diameter) and are propelled into skin cellsor muscle with a “gene gun.” It will be obvious to one of skill in theart that the number of doses administered to a patient is dependent uponthe goal of the administration (e.g., the extent of the disease and theresponse of an individual patient to the treatment). Therefore, it iswithin the scope of the present invention that a suitable number ofdoses includes any number required to regulate B lymphocyteproliferation, activation and/or survival, or to regulate a disease orcondition related thereto. Effective in vivo dose parameters can bedetermined using methods standard in the art. Such methods include, forexample, determination of survival rates, side effects (i.e., toxicity),determination of cellular and humoral immune response effects, and/oreffects on conditions related to B lymphocyte proliferation, activationand/or survival.

[0122] In the method of the present invention, TALL-1 and TALL-1receptor proteins (including homologues), antibodies, nucleic acidmolecules and/or mimetics, as well as compositions comprising suchcompounds can be administered to any member of the Vertebrate class,Mammalia, including, without limitation, primates, rodents, livestockand domestic pets. Livestock include mammals to be consumed or thatproduce useful products (e.g., sheep for wool production). Preferredmammals to protect include humans, dogs, cats, mice, rats, rabbits,sheep, cattle, horses and pigs, with humans being most preferred.According to the present invention, administration of a composition isuseful to regulate a target cell. Typically, it is desirable to modulateproliferation, activation, and/or survival of a B lymphocyte to obtain atherapeutic benefit in a patient. Patients whom are suitable candidatesfor the method of the present invention include, but are not limited to,patients that will benefit from reduced B lymphocyte proliferation,activation and/or survival, such as patients that have, or are at riskof developing (e.g., are predisposed to), autoimmune diseases, andimmunoproliferative diseases, as well as patients in need of enhanced Blymphocyte proliferation, activation or survival (e.g., patientsreceiving a vaccination or patients having a suppressed immune system).

[0123] Compositions of the present invention, and the compounds in suchcompositions, are useful in a variety of methods which make use of thediscovery that TALL-1 is the ligand for the TALL-1 (BCMA) receptor.Accordingly, one embodiment of the present invention relates to a methodto activate a TALL-1 receptor, comprising contacting a TALL-1 receptorwith a TALL-1 protein. In a preferred embodiment, the TALL-1 receptor isexpressed by a B lymphocyte. Such method can be performed in vitro, exvivo or in vivo. According to the present invention, reference to “Bcells” or “B lymphocytes” includes splenic B cells, lymph node B cells,myeloma cells, peripheral blood B cells, bone marrow B cells andhybridoma cells. Hybridoma cells refer to hybrid cell lines comprisingmyeloma cells (tumor cells capable of being maintained in tissue culturebut do not produce immunoglobulin) fused with, for example, a spleencell capable of producing an immunoglobulin molecule. The TALL-1 proteincan be any TALL-1 protein as previously described herein, including awild-type TALL-1 protein (membrane or soluble), a TALL-1 homologue, aTALL-1 fusion protein, or a TALL-1 peptide mimetic. The step ofcontacting can be by any suitable method, including any of the methodsof administration or delivery described above. Preferably, the TALL-1receptor is contacted with the TALL-1 protein in a manner such that theTALL-1 protein can bind to the receptor, and thereby activate thereceptor. TALL-1 receptor activation can be detected using any suitablemethod including, but not limited to, detection of increased TALL-1receptor transcription, detection of increased TALL-1 receptortranslation, detection of increased NFκB activation, detection of theactivation of TRAF5, TRAF6, NIK, IKKα or IKKβ, detection of B cellproliferation, detection of B cell survival. Many of such methods aredescribed in detail in the Examples section, and suitable methods forall such steps of detection are known in the art.

[0124] Yet another embodiment of the present invention relates to amethod to regulate B lymphocyte proliferation, activation, or survival.Such a method includes the step of regulating the biological activity ofa TALL-1 receptor, wherein the TALL-1 receptor is expressed by a Blymphocyte. According to the present invention, to regulate thebiological activity of a TALL-1 receptor refers to upregulating (e.g.,stimulating, enhancing, increasing) the biological activity of thereceptor or to downregulating (e.g., decreasing, reducing, inhibiting)the biological activity of the receptor. As described above, abiological activity of a TALL-1 receptor includes, costimulation of Bcell proliferation, costimulation of B cell activation, and/orenhancement of B cell survival, as well as more particular activitiessuch as NFκB activation or activation of TRAF5, TRAF6, NIK, IKKα orIKKβ.

[0125] In one embodiment of the present invention, this method of thepresent invention is used to inhibit the biological activity of theTALL-1 receptor. TALL-1 receptor activity can be inhibited, for example,by inhibiting the interaction of TALL-1 with the TALL-1 receptor. Suchinhibition can be achieved by any suitable means of inhibiting theinteraction between TALL-1 and TALL-1 receptor including, but notlimited to, downregulating expression of TALL-1 (e.g., by inhibition ofmacrophages or monocyte activity, by antisense methods, by ribozymemethods, etc.), downregulating expression of the TALL-1 receptor (e.g.,by inhibition of B cell activity, by antisense methods, by ribosymemethods, etc.), and/or by physically blocking the interaction.

[0126] In one aspect, the step of inhibiting comprises contacting TALL-1expressed by a monocyte or macrophage with a compound that inhibitsbinding of the TALL-1 to the TALL-1 receptor. Such a compound caninclude, but is not limited to: (a) an antibody that selectively bindsto TALL-1 and inhibits the binding of TALL-1 to the TALL-1 receptor; (b)a soluble TALL-1 receptor; and, (c) a TALL-1 receptor homologue,including any of the TALL-1 receptor homologues described herein. Inthis aspect, a TALL-1 receptor homologue preferably binds to TALL-1, butdoes not activate signal transduction molecules, such as NF-κB, in a Blymphocyte, when expressed by such a cell. Such a homologue can competewith a wild-type TALL-1 receptor for the binding to TALL-1. In oneembodiment, such a homologue binds to TALL-1 with a greater affinitythan does the wild-type TALL-1 receptor. Such a compound can alsoinclude TALL-1 receptor mimetics that are capable of binding to TALL-1but which do induce TALL-1 receptor biological activity.

[0127] In another aspect of this method, the step of inhibitingcomprises contacting the TALL-1 receptor with a compound that inhibitsthe interaction of TALL-1 with the TALL-1 receptor. The TALL-1 receptoris expressed by a B lymphocyte. Such a compound can include, but is notlimited to: (a) an antibody that selectively binds to the TALL-1receptor and inhibits the binding of the TALL-1 receptor by TALL-1; and(b) a TALL-1 homologue, including any of the TALL-1 homologues describedherein. Preferably, such a homologue binds to the TALL-1 receptor butdoes not activate the TALL-1 receptor. The compound can also includeTALL-1 mimetics that are capable of binding to a TALL-1 receptor, butwhich do not induce TALL-1 receptor biological activity.

[0128] In some embodiments, it is desirable to regulate TALL-1 receptoractivity, and thus B lymphocyte activity, by increasing the biologicalactivity of the TALL-1 receptor. TALL-1 receptor activity can beincreased, for example, by increasing the interaction of TALL-1 with theTALL-1 receptor. Such an increase can be achieved by any suitable meansof upregulating the interaction between TALL-1 and TALL-1 receptorincluding, but not limited to, upregulating expression of TALL-1 (e.g.,by stimulation of macrophages or monocyte activity), upregulatingexpression of the TALL-1 receptor (e.g., by stimulation of B cellactivity or genetically engineering B lymphocytes to overexpress TALL-1receptor), and/or by physically inducing or increasing the interactionbetween TALL-1 and TALL-1 receptor. In one embodiment, such a methodincludes contacting the TALL-1 receptor with a compound that increasesTALL-1 receptor activity. Such a compound can include, but is notlimited to: (a) an isolated TALL-1 protein; and, (b) an antibody thatselectively binds to the TALL-1 receptor and activates the receptor. Anisolated TALL-1 protein can include any TALL-1 protein, including TALL-1homologues, described herein. The TALL-1 homologue binds to a TALL-1receptor in a manner effective to activate the TALL-1 receptor, whensuch receptor is expressed by a B lymphocyte. Such a compound can alsoinclude TALL-1 mimetics that bind to and activate a TALL-1 receptor.

[0129] Preferably, regulation of B lymphocyte proliferation by themethod is effective to regulate a B-lymphocyte immune response in ananimal. For example, when upregulation of a B lymphocyte immune responseis desired, such as when a patient is vaccinated, or when a patient hasa suppressed B cell response due to disease or stress, the interactionbetween TALL-1 and TALL-1 receptor is preferably increased. Whendownregulation of a B lymphocyte immune response is desired, such aswhen a patient has an autoimmune disease, and particularly an autoimmunedisease in which autoreactive B lymphocytes play a prominent role, theinteraction between TALL-1 and TALL-1 receptor is preferably decreased.

[0130] According to the present invention, the method of the presentinvention is primarily directed to the regulation of the biologicalactivity of a target cell (i.e., a B lymphocyte, a monocyte or amacrophage) in a patient with the added, but not required, goal ofproviding some therapeutic benefit to a patient. Modulating thephenotype of a target cell in a patient in the absence of obtaining sometherapeutic benefit is useful for the purposes of determining factorsinvolved (or not involved) in a disease and preparing a patient to morebeneficially receive another therapeutic composition. In a preferredembodiment, however, the methods of the present invention are directedto the modulation of the phenotype of a target cell which is useful inproviding some therapeutic benefit to a patient. As such, a therapeuticbenefit is not necessarily a cure for a particular disease or condition,but rather, preferably encompasses a result which can includealleviation of the disease or condition, elimination of the disease orcondition, reduction of a symptom associated with the disease orcondition, prevention or alleviation of a secondary disease or conditionresulting from the occurrence of a primary disease or condition, and/orprevention of the disease or condition. As used herein, the phrase“protected from a disease” refers to reducing the symptoms of thedisease; reducing the occurrence of the disease, and/or reducing theseverity of the disease. Protecting a patient can refer to the abilityof a composition of the present invention, when administered to apatient, to prevent a disease from occurring and/or to cure or toalleviate disease symptoms, signs or causes. As such, to protect apatient from a disease includes both preventing disease occurrence(prophylactic treatment) and treating a patient that has a disease(therapeutic treatment) to reduce the symptoms of the disease. Inparticular, protecting a patient from a disease or enhancing anothertherapy (e.g., vaccination) is accomplished by regulating theinteraction between TALL-1 and TALL-1 receptor such that a beneficialeffect is obtained. A beneficial effect can easily be assessed by one ofordinary skill in the art and/or by a trained clinician who is treatingthe patient. The term, “disease” refers to any deviation from the normalhealth of a mammal and includes a state when disease symptoms arepresent, as well as conditions in which a deviation (e.g., infection,gene mutation, genetic defect, etc.) has occurred, but symptoms are notyet manifested.

[0131] In one embodiment, by performing the method of the presentinvention, the interaction between TALL-1 and TALL-1 receptor isdeceased, such a decrease being sufficient to downregulate B lymphocyteproliferation, activation and/or survival in a patient (or in a culture,if the method is performed in vitro or ex vivo). In one embodiment, whenthe target cell is an autoreactive B lymphocyte, typically, the patienthas or is at risk of developing an autoimmune disease associated withthe autoreactive B lymphocyte. Such autoimmune diseases can be anyautoimmune disease, and particularly include, rheumatoid arthritis,systemic lupus erythematosus, insulin dependent diabetes mellitis,multiple sclerosis, myasthenia gravis, Grave's disease, autoimmunehemolytic anemia, autoimmune thrombocytopenia purpura, Goodpasture'ssyndrome, pemphigus vulgaris, acute rheumatic fever, post-streptococcalglomerulonephritis, or polyarteritis nodosa. The autoreactive Blymphocyte in such a patient, prior to the step of administering thecomposition of the present invention, generally has normal or enhancedproliferation, activation, and/or survival as compared to a B lymphocytefrom a patient that does not have and is not at risk of developing theautoimmune disease.

[0132] Inhibition of the interaction between TALL-1 and TALL-1 receptorexpressed by an autoreactive B lymphocyte can result in a reduction inthe proliferation, activation and/or survival of the B lymphocyte, whichcan be detected as a change in: B lymphocyte cytokine production, areduction in NFκB activation, a reduction in TRAF5, TRAF6, NIK, IKKα andIKKβ activation, a reduction in immunoglobulin maturation, a reductionin immunoglobulin production and secretion, a reduction in calciummobilization, or a reduction in phosphorylation of signal transductionproteins. Preferably, inhibition of the interaction between TALL-1 andTALL-1 receptor in the B lymphocytes of the patient produces a result inthe patient which includes, but is not limited to, decreasedautoantibody production, decreased autoreactive B cell proliferation,decreased autoreactive B cell survival, and/or reduced destruction ofautologous cells or tissues, as compared to any of these measurementsprior to the conducting of the method of the present invention, or ascompared to a patient with the disease who has not been administered thecomposition of the present invention.

[0133] In one embodiment, by performing the method of the presentinvention, the interaction between TALL-1 and TALL-receptor isincreased, such an increase being sufficient to upregulate B lymphocyteproliferation, activation and/or survival in a patient (or in a culture,if the method is performed in vitro or ex vivo). In one embodiment, thetarget cell is a normal B lymphocyte (e.g., in a patient receiving avaccination), an anergic B lymphocyte, or a B lymphocyte in a patientsuffering from a suppressed humoral immune response (e.g., in an immunecompromised patient). The B lymphocyte in such a patient, prior to thestep of administering the composition of the present invention,generally has normal or reduced proliferation, activation, and/orsurvival as compared to a B lymphocyte from a normal individual, to apatient who is not immune compromised, or to a patient that does nothave and is not at risk of developing the disease.

[0134] Increasing the interaction between TALL-1 and TALL-1 receptorexpressed by a normal or suppressed B lymphocyte can result in anincrease in the proliferation, activation and/or survival of the Blymphocyte, which can be detected as a change in: B lymphocyte cytokineproduction, an increase in NFκB activation, an increase in TRAF5, TRAF6,NIK, IKKα and IKKβ activation, an increase in immunoglobulin maturation,an increase in immunoglobulin production and secretion, an increase incalcium mobilization, and/or an increase in phosphorylation ofintracellular signal transduction proteins. Preferably, increasing theinteraction between TALL-1 and TALL-1 receptor in the B lymphocytes ofthe patient produces a result in the patient which includes, but is notlimited to, increased antibody production, increased B cellproliferation, and increased B cell survival, as compared to any ofthese measurements prior to the conducting of the method of the presentinvention, or as compared to a patient with the disease who has not beenadministered the composition of the present invention.

[0135] Yet another embodiment of the present invention relates to amethod to identify compounds that regulate B lymphocyte proliferation,activation and/or survival by regulating the interaction between TALL-1and a TALL-1 receptor. In one embodiment, the method can be a cell-freeor a cell-based assay which includes the steps of: (a) contacting aTALL-1 receptor with a putative regulatory compound; (b) contacting theTALL-1 receptor with a TALL-1 protein; and (c) detecting whether theTALL-1 protein is capable of binding to the receptor in the presence ofthe putative regulatory compound as compared to in the absence of theputative regulatory compound. In another embodiment, the method includesthe steps of: (a) contacting a TALL-1 protein with a putative regulatorycompound; (b) contacting the TALL-1 protein with a TALL-1 receptor; and,(c) detecting whether the TALL-1 protein is capable of binding to thereceptor in the presence of the putative regulatory compound as comparedto in the absence of the putative regulatory compound. Preferably, step(a) is performed prior to step (b) in these embodiments. In one aspect,an additional step can be performed prior to step (b) to determinewhether the putative compound regulates (binds to and/or activates)TALL-1 or TALL-1 receptor activity directly. In these embodiments, theTALL-1 protein can be soluble or otherwise cell-free (e.g., the membraneform separate from cell membranes); expressed by a cell, such as amonocyte, macrophage, or other cell capable of expressing TALL-1; orprovided in a cell lysate. The TALL-1 receptor can be provided as asoluble protein or otherwise cell-free (e.g., in the absence of cellmembranes); expressed by a cell, such as a B lymphocyte, or other cellcapable of expressing TALL-1 receptor; or in a cell lysate.

[0136] In these embodiments, reduced binding of TALL-1 to its receptorin the presence of the putative regulatory compound as compared to inthe absence of the compound indicates that the putative regulatorycompound is an inhibitor of TALL-1 and TALL-1 receptor interaction. Thecompound can be further tested, if desired, in a cell-based assay todetermine whether the compound inhibits the biological activity of theTALL-1 receptor, as determined by a reduction in TALL-1 biologicalactivity as previously described herein. Similarly, in this embodiment,increased binding of TALL-1 to its receptor in the presence of theputative regulatory compound as compared to in the absence of thecompound indicates that the putative regulator is an enhancer of TALL-1and TALL-1 receptor interaction. If no change in the binding of TALL-1to its receptor is detected in the presence of the putative regulatorycompound as compared to in the absence of the compound, one can concludethat the compound does not appear to affect the binding of TALL-1 to itsreceptor. In this instance, a cell-based assay can be used to detectwhether the putative regulatory compound increases or decreases thebiological activity of a TALL-1 receptor.

[0137] In further embodiment of the method of the present invention,such a method is a cell-based assay which includes the steps of: (a)contacting a B lymphocyte expressing a TALL-1 receptor with a putativeregulatory compound; (b) contacting the B lymphocyte with a TALL-1protein as previously described herein; and, (c) detecting whether theputative regulatory compound regulates the TALL-1 receptor.Alternatively, the method can include the steps of: (a) contacting amacrophage or monocyte expressing a TALL-1 protein, or alternatively,contacting a TALL-1 protein in the absence of a cell (e.g., solubleTALL-1), with a putative regulatory compound; (b) contacting the TALL-1protein (expressed by a cell or cell-free) with a TALL-1 receptorprotein expressed by a B lymphocyte; and, (c) detecting whether theputative regulatory compound regulates the TALL-1 receptor. Preferably,step (a) is performed prior to step (b) in these embodiments. In oneaspect, an additional step can be performed prior to step (b) todetermine whether the putative compound regulates (binds to and/oractivates) TALL-1 or TALL-1 receptor activity directly. In this assay,the TALL-1 protein can be soluble or otherwise cell-free (e.g., themembrane form separate from cell membranes); expressed by a cell, suchas a monocyte, macrophage, or other cell capable of expressing TALL-1;or provided in a cell lysate. The TALL-1 receptor is expressed by acell, such as a B lymphocyte, or other cell capable of expressing TALL-1receptor.

[0138] In these embodiments, reduced binding of TALL-1 to its receptorand/or reduced TALL-1 receptor biological activity in the presence ofthe putative regulatory compound as compared to in the absence of thecompound indicates that the putative regulatory compound is an inhibitorof TALL-1 and TALL-1 receptor interaction, and/or an inhibitor of TALL-1receptor biological activity. Similarly, in this embodiment, increasedbinding of TALL-1 to its receptor and/or increased TALL-1 receptorbiological activity in the presence of the putative regulatory compoundas compared to in the absence of the compound indicates that theputative regulator is an enhancer of TALL-1 and TALL-1 receptorinteraction and/or of TALL-1 biological activity. If no change in thebinding of TALL-1 to its receptor is detected in the presence of theputative regulatory compound as compared to in the absence of thecompound, one can conclude that the compound does not appear to affectthe binding of TALL-1 to its receptor, although an increase or decreasein the biological activity of a TALL-1 receptor may still be detected.

[0139] As used herein, the term “putative” refers to compounds having anunknown or previously unappreciated regulatory activity in a particularprocess. As such, the term “identify” is intended to include allcompounds, the usefulness of which as a regulatory compound of theinteraction between TALL-1 and TALL-1 receptor for the purposes ofregulating B lymphocyte proliferation, activation and/or survival isdetermined by a method of the present invention.

[0140] The methods of the present invention include contacting a TALL-1protein and/or a TALL-1 receptor with a compound being tested for itsability to bind to TALL-1 or TALL-1 receptor and/or to regulate theactivity of TALL-1 and/or its receptor, such as by blocking theinteraction between the ligand and receptor. The step of contacting canbe performed by any suitable method, depending on how the TALL-1 and/orTALL-1 receptor are provided. For example, cells expressing TALL-1 orTALL-1 receptor can be grown in liquid culture medium or grown on solidmedium in which the liquid medium or the solid medium contains thecompound to be tested. In addition, as described above, the liquid orsolid medium contains components necessary for cell growth, such asassimilable carbon, nitrogen and micro-nutrients. Cell lysates can becombined with other cell lysates and/or the compound to be tested in anysuitable medium. In another embodiment, the TALL-1 protein and/or theTALL-1 receptor and/or cell lysates containing such proteins can beimmobilized on a substrate such as: artificial membranes, organicsupports, biopolymer supports and inorganic supports. The protein can beimmobilized on the solid support by a variety of methods includingadsorption, cross-linking (including covalent bonding), and entrapment.Adsorption can be through van del Waal's forces, hydrogen bonding, ionicbonding, or hydrophobic binding. Exemplary solid supports for adsorptionimmobilization include polymeric adsorbents and ion-exchange resins.Solid supports can be in any suitable form, including in a bead form,plate form, or well form.

[0141] The present methods involve contacting cells with the compoundbeing tested for a sufficient time to allow for interaction, activationor inhibition of the TALL-1 protein or TALL-1 receptor by the compound.The period of contact with the compound being tested can be varieddepending on the result being measured, and can be determined by one ofskill in the art. For example, for binding assays, a shorter time ofcontact with the compound being tested is typically suitable, than whenactivation is assessed. As used herein, the term “contact period” refersto the time period during which the proteins are in contact with thecompound being tested and/or the time period during which the TALL-1protein and the TALL-1 receptor are in contact (or in a condition wherecontact is possible) with each other. The term “incubation period”refers to the entire time during which, for example, cells are allowedto grow prior to evaluation, and can be inclusive of the contact period.Thus, the incubation period includes all of the contact period and mayinclude a further time period during which the compound being tested isnot present but during which growth is continuing (in the case of a cellbased assay) prior to scoring. The incubation time for growth of cellscan vary but is sufficient to allow for the binding of the TALL-1receptor, activation of the receptor, and/or inhibition of the receptor.It will be recognized that shorter incubation times are preferablebecause compounds can be more rapidly screened. A preferred incubationtime is between about 1 minute to about 48 hours.

[0142] The conditions under which the cell or cell lysate of the presentinvention is contacted with a putative regulatory compound and/or withother cells or cell lysates, such as by mixing, are any suitable cultureor assay conditions and includes an effective medium in which the cellcan be cultured or in which the cell lysate can be evaluated in thepresence and absence of a putative regulatory compound. Similarly, theconditions under which soluble TALL-1 and/or TALL-1 receptors arecontacted with a putative regulatory compound and/or with each other areany suitable assay conditions, such as by immobilization of the ligandor receptor on a substrate in conditions under which the ligand and/orreceptor can contact the putative regulatory compound prior to,simultaneously with, or after contact of the ligand and receptor witheach other.

[0143] Cells of the present invention can be cultured in a variety ofcontainers including, but not limited to, tissue culture flasks, testtubes, microtiter dishes, and petri plates. Culturing is carried out ata temperature, pH and carbon dioxide content appropriate for the cell.Such culturing conditions are also within the skill in the art.Acceptable protocols to contact a cell with a putative regulatorycompound in an effective manner include the number of cells percontainer contacted, the concentration of putative regulatorycompound(s) administered to a cell, the incubation time of the putativeregulatory compound with the cell, and the concentration of compoundadministered to a cell. Determination of such protocols can beaccomplished by those skilled in the art based on variables such as thesize of the container, the volume of liquid in the container, the typeof cell being tested and the chemical composition of the putativeregulatory compound (i.e., size, charge etc.) being tested. A preferredamount of putative regulatory compound(s) comprises between about 1 nMto about 10 mM of putative regulatory compound(s) per well of a 96-wellplate.

[0144] Suitable cells for use with the present invention include anycell that endogenously expresses a TALL-1 receptor or a TALL-1 proteinas disclosed herein (such as a B lymphocyte for TALL-1 receptor or amonocyte or macrophage for TALL-1 protein), or which has beentransfected with and expresses recombinant TALL-1 receptor or TALL-1protein as disclosed herein (such as 293 cells, COS cells, CHO cells,fibroblasts, etc., genetically engineered to express TALL-1 or TALL-1receptor). In one embodiment, host cells genetically engineered toexpress a functional receptor that responds to activation by TALL-1protein can be used as an endpoint in the assay; e.g., as measured by achemical, physiological, biological, or phenotypic change, induction ofa host cell gene or a reporter gene, change in cAMP levels, adenylylcyclase activity, host cell G protein activity, host cell kinaseactivity, proliferation, differentiation, etc. Cells for use with thepresent invention include mammalian, invertebrate, plant, insect,fungal, yeast and bacterial cells. Preferred cells include mammaliancells. Preferred mammalian cells include primate, non-human primate,mouse and rat, with human cells being preferred. Preferably, the testcell (host cell) should express a functional TALL-1 receptor that givesa significant response to interaction with a TALL-1 protein that isknown to bind to and activate the TALL-1 receptor, preferably greaterthan 2, 5, or 10-fold induction over background.

[0145] The TALL-1 protein can be contacted with the TALL-1 receptor (orthe cell expressing such receptor) prior to, simultaneous with, or aftercontact of the putative regulatory compound with the cell, depending onhow the assay is to be evaluated, and depending on whether activation orinhibition of the receptor and/or cell expressing the receptor is to beevaluated. In one embodiment, the TALL-1 protein is contacted with theTALL-1 receptor after the cell is contacted with the putative regulatorycompound so that the test compound can be evaluated for its ability toinhibit activation of the receptor by the TALL-1 protein. In anotherembodiment, when binding is to be evaluated, the TALL-1 protein can becontacted with the TALL-1 receptor at the same time as the testcompound. Preferably, the TALL-1 protein is contacted with thecell/TALL-1 receptor in the presence and absence of the test compoundfor a controlled assay.

[0146] As discussed above, the step of detecting whether a putativeregulatory compound binds to, activates and/or inhibits the interactionbetween TALL-1 and its receptor can be performed by any suitable method,including, but not limited to measurement of TALL-1 receptortranscription, measurement of TALL-1 receptor translation, measurementof phosphorylation of the TALL-1 receptor, measurement of TALL-1receptor binding to TALL-1, measurement of TALL-1 receptor translocationwithin a cell, measurement of NFκB activation, measurement of TRAF5,TRAF6, NIK, IKKα and/or IKKβ activation, measurement of B cellproliferation, measurement of B cell activation, and measurement of Bcell survival. Such methods of detecting an interaction of a ligand witha receptor are known in the art, and include immunoblots,phosphorylation assays, kinase assays, immunofluorescence microscopy,RNA assays, immunoprecipitation, and other biological assays.

[0147] As disclosed above, the present methods also make use of non-cellbased assay systems to identify compounds that can regulate theinteraction between TALL-1 and TALL-1 receptor. For example, isolatedmembranes may be used to identify compounds that interact with theTALL-1 receptor being tested. Membranes can be harvested from cellsexpressing TALL-1 receptors by standard techniques and used in an invitro binding assay. ¹²⁵I-labeled ligand (e.g., ¹²⁵I-labeled TALL-1) isbound to the membranes and assayed for specific activity; specificbinding is determined by comparison with binding assays performed in thepresence of excess unlabeled ligand. Membranes are typically incubatedwith labeled ligand in the presence or absence of test compound (i.e., aputative regulatory compound). Compounds that bind to the receptor andcompete with labeled ligand for binding to the membranes reduced thesignal compared to the vehicle control samples.

[0148] Alternatively, soluble TALL-1 receptors may be recombinantlyexpressed and utilized in non-cell based assays to identify compoundsthat bind to TALL-1 receptors. Recombinantly expressed TALL-1 receptorpolypeptides or fusion proteins containing one or more extracellulardomains of TALL-1 receptor can be used in the non-cell based screeningassays. Alternatively, peptides corresponding to a cytoplasmic domain ofthe TALL-1 receptor or fusion proteins containing a cytoplasmic domainof the TALL-1 receptor can be used in non-cell based assay systems toidentify compounds that bind to the cytoplasmic portion of the TALL-1receptor; such compounds may be useful to modulate the signaltransduction pathway of the TALL-1 receptor. In non-cell based assaysthe recombinantly expressed TALL-1 receptor is attached to a solidsubstrate such as a test tube, microtiter well or a column, by meanswell known to those in the art. The test compounds are then assayed fortheir ability to bind to the TALL-1 receptor.

[0149] As discussed above, in vitro cell based assays may be designed toscreen for compounds that regulate TALL-1 receptor expression at eitherthe transcriptional or translational level. In one embodiment, DNAencoding a reporter molecule can be linked to a regulatory element ofthe TALL-1 receptor gene and used in appropriate intact cells, cellextracts or lysates to identify compounds that modulate TALL-1 receptorgene expression. Appropriate cells or cell extracts are prepared fromany cell type that normally expresses the TALL-1 receptor gene, therebyensuring that the cell extracts contain the transcription factorsrequired for in vitro or in vivo transcription. The screen can be usedto identify compounds that modulate the expression of the reporterconstruct. In such screens, the level of reporter gene expression isdetermined in the presence of the test compound and compared to thelevel of expression in the absence of the test compound.

[0150] In any of the above-described methods of the present invention,the TALL-1 protein can be any TALL-1 protein described herein, includinghomologues that are capable of binding to and/or activating the receptorin the absence of the putative regulatory compound. Similarly, theTALL-1 receptor can be any TALL-1 receptor described herein, includinghomologues that are capable of binding to TALL-1 and/or being activatedby a TALL-1 protein in the absence of a putative regulatory compound.

[0151] The following examples are provided for the purposes ofillustration and are not intended to limit the scope of the presentinvention.

EXAMPLES Example 1

[0152] The following example describes the identification and cloning ofa nucleic acid sequence encoding TALL-1.

[0153] To identify novel members of the TNF family, the presentinventors searched the GenBank EST database using the TBLASTN programfor genes that were homologous to the extracellular domains of humantumor necrosis factor (TNF) and Fas ligand (FasL/ApoL). This searchidentified multiple EST clones that apparently encoded portions of twodifferent human genes. These EST clones had the following GenBankAccession Nos.: AA682496, R16882, AI749928, AA166695, and T87299. Thepresent inventors designated the first gene as Tall-1 (for TNF- andApoL-related Leukocyte-expressed Ligand 1, see below). Sequence analysisof the above-described EST clones suggested that they were partialclones. To clone the full length Tall-1 cDNA, one of the EST clones wasobtained (GenBank accession number AA682496) through the I.M.A.G.E.consortium. This EST clone was identified as a Soares fetal liver spleenINFLS S1 Homo sapiens cDNA clone. The present inventors screened a humanperipheral blood leukocyte cDNA library, using the EST clones as a probe(GenBank accession number AA682496). Subsequent sequence analysis of thelongest five positive clones obtained with this screening indicated thatTall-1 encodes a 285 amino acid protein, having an amino acid sequencerepresented herein as SEQ ID NO:2. The complete nucleic acid sequenceencoding SEQ ID NO:2 is represented herein as SEQ ID NO:1. The GenBankAccession No. for the nucleic acid sequence encoding human TALL-1 isAF136293. The GenBank Accession No. for the amino acid sequence of thehuman TALL-1 protein is AAD29421.

[0154] With regard to the above-identified EST clones (GenBank AccessionNos.: AA682496, R16882, AI749928, AA166695, T87299), the followinghomology to SEQ ID NO:1 was noted, using BLAST 2 alignment with theOBLOSUM62 matrix as described elsewhere herein. The nucleic acidsequence of EST clone AA682496 (positions 80 to 456), a human Soaresfetal liver spleen INFLS_S1 cDNA clone, is 100% identical to the reversecomplement of nucleotide positions 482 to 858 (377 nucleotides) of SEQID NO:1. The nucleic acid sequence of EST clone R16882 (positions 89 to360), a human Soares fetal liver spleen cDNA clone, is 94% identical tothe reverse complement of nucleotide positions 592 to 858 (267nucleotides) of SEQ ID NO:1. The nucleic acid sequence of EST cloneAI749928 (positions 75 to 437), a human Barstead aorta cDNA clone, was100% identical to the reverse complement of nucleotide positions 496 to858 (363 nucleotides) of SEQ ID NO:1. The nucleic acid sequence of ESTclone AA166695 (positions 81 to 446), a Stratagene ovarian cancer humancDNA clone, was 98% identical to the reverse complement of nucleotidepositions 489 to 858 (370 nucleotides) of SEQ ID NO:1. The nucleic acidsequence of EST clone T87299 (positions 96 to 363), a Soares fetal liverspleen human cDNA clone, was 94% identical to the reverse complement ofnucleotide positions 596 to 858 (263 nucleotides) of SEQ ID NO:1.

[0155] Structural analysis of the SEQ ID NO:2 suggests that TALL-1 is atype II transmembrane protein. The C-terminal part of the extracellulardomain of TALL-1 shares approximately 20-25% sequence identity with thecorresponding domains of TNF (FIG. 1B, SEQ ID NO:4), FasL (FIG. 1B, SEQID NO:5), Lymphotoxin-α (FIG. 1B, SEQ ID NO:6), and TRAIL (FIG. 1B, SEQID NO:7). Referring to FIG. 1B, the conserved P-strands are underlined,and homologous regions are boxed with identical residues shaded. FIG. 1Bshows that the sequence homology is primarily limited to the residuesforming several β-strands. These data suggest that TALL-1 is a member ofthe TNF family, and like some other members of the TNF family, foldsinto an anti-parallel β-sandwich structure (Banner et al., (1993), Cell73:431-445; Eck et al., (1989), J. Biol. Chem. 267:2119-2122).

[0156] Sequence analysis of the EST clones encoding the second TNF/FasLlike gene, which the present inventors designated as TALL-2, indicatedthat this gene is identical to the recently described molecule APRIL(Hahne et al., (1998), J. Exp. Med. 188:1185-1190). The GenBankAccession No. for the nucleic acid sequence encoding TALL-2 is AF136294. The GenBank Accession No. for the TALL-2 protein is AAD29422.The C-terminal region of the extracellular domain of TALL-2/APRIL (FIG.1B, SEQ ID NO:3) also shares about 20-25% sequence identity with thoseof TNF, FasL, TRAIL and Lymphotoxin-α. Interestingly, as shown in FIG.1A, the C-terminal regions of the extracellular domains of TALL-1 (SEQID NO:2) and TALL-2/APRIL (SEQ ID NO:3) share ˜35% sequence identitywith each other, significantly higher than with other members of the TNFfamily. Referring to FIG. 1A, the putative transmembrane domains ofTALL-1 and TALL-2/APRIL are underlined, and homologous regions are boxedwith identical residues shaded. In addition to the C-terminal regions ofthe extracellular domains, the homology between TALL-1 and TALL-2/APRILextends to other parts of the molecules, including the N-terminal regionof the extracellular domains, the transmembrane and the intracellulardomains (FIG. 1A). This data suggests that TALL-1 and TALL-2/APRILbelong to a subfamily of the TNF family of ligands.

[0157] Northern blot analysis suggested that human TALL-1 is expressedabundantly in peripheral blood leukocytes (PBLs) and weakly in spleen asa single 2.4 kb transcript (FIG. 2A). Briefly, multiple human tissueblots were purchased from Clontech and were hybridized under highstringency conditions according to the manufacturer. Specifically, theblots were hybridized with Clontech's Rapid Hybridization Buffer at 68°C. for 2 hours. The blots were washed in 2×SSC/0.1% SDS at roomtemperature for 10 minutes, followed by 0.1×SSC/0.1% SDS at 68° C. for30 minutes. The molecular size standards (in kilobases) are shown inFIG. 2A on the left. FIG. 2A shows that TALL-1 is barely detectable inall other tissues examined (FIG. 2A). Interestingly, Northern blotanalysis indicated that the highest level of APRIL is also detected inperipheral blood leukocytes (data not shown, Tan et al., (1997), Gene204:35-46).

[0158] To identify the specific cell types in PBLs that express TALL-1,the present inventors performed reverse transcriptase-polymerase chainreaction (RT-PCR) analysis with RNAs extracted from isolated humanperipheral monocytes, macrophages, T and B lymphocytes. Briefly, humanperipheral blood monocytes and macrophages were isolated as described(Nedwin et al., (1985), J. Immunol. 135:2492-2498). Human peripheral Tlymphocytes were isolated from monocyte/macrophage depleted lymphocytesusing anti-CD2 magnetic beads (Dynal, Inc.) by following proceduressuggested by the manufacture. B cells were isolated by T cell deletionof the lymphocytes. The isolated cells were treated with PMA (10ng/ml)/ionomycin (500 ng/ml) for 4 or 10 hours, or left untreated. TotalRNAs were then extracted and RT-PCR experiments were performed with theprimers corresponding to the sequences of TALL-1 or β-actin cDNAs, usinga standard protocol as described in Sambrook et al. This experimentdemonstrated that TALL-1 was constitutively expressed in untreatedmonocytes and macrophages, but not in peripheral T and B lymphocytes(FIG. 2B). The mRNA level of TALL-1 was down-regulated by PMA/ionomycintreatment in both monocytes and macrophages (FIG. 2B). Similarly, it wasdetermined that TALL-2/APRIL was also specifically expressed inmonocytes and macrophages, and its expression was downregulated byPMA/ionomycin treatment (data not shown).

[0159] Consistent with these observations, Northern blot analysis showedthat TALL-1 was abundantly and constitutively expressed in the monocyticcell line U937, but not in the T cell line Jurkat (FIG. 3). Briefly,U937 and Jurkat cells were treated with recombinant human tumor necrosisfactor (TNF; 20 ng/ml), interferon-γ (IFN-γ; 20 ng/ml), interleukin-2(IL-2; 20 units/ml), phorbol myristate acetate (PMA; 10 ng/ml)/ionomycin(500 ng/ml), or IL-2 plus PMA/ionomycin for 10 hours, or left untreated.Cells were then harvested and total RNAs were isolated for Northern blotanalysis with human Tall-1 cDNA probe. The same blots were stripped andreprobed with human α-actin probe. In U937 cells, TALL-1 expression wasalso dramatically down-regulated by PMA/ionomycin, while TNF, IFN-γ, andIL-2 had no effect on TALL-1 expression (FIG. 3). These data aresurprising in that many TNF family members, such as TNF, FasL,Lymphotoxin-α, and LIGHT, are mostly expressed in activated, butminimally or not at all in unstimulated immune cells, and areup-regulated by mitogens (Mauri et al., (1998), Immunity 8:21-30;Svedersky et al., J. Immunol. 134:1604-1608; Nedwin et al., (1985), J.Immunol. 135:2492-2498).

[0160] To determine whether TALL-1 gene encodes an expressed protein, apeptide-directed rabbit polyclonal antibody was raised against afragment of the extracellular domain of TALL-1. Immunoprecipitation andwestern blot experiments with this antibody indicated that TALL-1 isexpressed as a ˜52 kDa protein in U937 cells (FIG. 4). Briefly, lysatesof U937 cells (1×10⁷) were immunoprecipitated with 1 ml preimmune serumcontrol or a rabbit polyclonal antibody against human TALL-1. Theimmunoprecipitates were analyzed by western blot with the TALL-1antibody. The molecular size standards (kDa) are shown to the left inFIG. 4 (IgG-H=IgG heavy chain; Ig-L=IgG light chain; pre=preimmuneserum; αTALL-1=anti-TALL-1 antibody). The molecular weight of the TALL-1protein detected was larger than that which was deduced from the aminoacid sequence. This may be due to its post-translational modification byglycosidation, which is true for most, if not all members of the TNFfamily.

[0161] TALL-1 and TALL-2/APRIL, either alone or together, do not induceapoptosis or NF-κB and AP1 activation in several cell lines, including293, Jurkat, and U937 (data not shown). The intracellular signalingpathways and the biological effects triggered by TALL-1 are described inmore detail in the examples below. TALL-1 and its receptor, TALL-1receptor, are clearly involved in monocyte/macrophage andB-lymphocyte-mediated immunological processes. Modify according to whatis now known.

Example 2

[0162] The following example demonstrates that TALL-1co-immunoprecipitates with B Cell Maturation Protein (BCMA).

[0163] To identify the receptor for TALL-1, the present inventorsemployed a candidate approach. Since all identified TNF family membersbind to receptors belonging to the TNF receptor family, the presentinventors speculated that the receptor for TALL-1 would also be a memberof the TNF receptor family whose expression is limited to B lymphocytes.Previously, a TNF receptor family member, B Cell Maturation Protein(BCMA), was identified during the analysis of a t(4;1)(q26;13)chromosomal translocation occurred in a human malignant T cell lymphoma(Laabi et al., (1992), EMBO J. 11:3897-3904). The breakpoints of the twochromosome partners involve the IL-2 gene on chromosome 4 and the BCMAgene on chromosome 16. The translocation results in the transcription ofa hybrid IL-2-BCMA mRNA composed of the first three exons of IL-2 at the5′ end fused to the coding sequences of BCMA mRNA at the 3 end (Laabi etal., (1992), EMBO J. 11:3897-3904). RNA protection analysis indicatesthat BCMA mRNA is expressed in most B lymphocyte-derived but not innon-B lymphocyte-derived cell lines (Laabi et al., (1994), Nucleic AcidsResearch 22:1147-1154; Gras et al., (1995), International Immunology7:1093-1106). In human tissues, BCMA is expressed by spleen and lymphnodes, but not by brain, muscle, heart, lung, kidney, pancreas, testis,and placenta. Using human malignant B cell lines characteristic ofdifferent stages of B lymphocyte differentiation, it has been shown thatBCMA mRNA is absent in the pro-B lymphocyte stage and its expressionincreases with B lymphocyte maturation (Laabi et al., (1994), NucleicAcids Research 22:1147-1154; Gras et al., (1995), InternationalImmunology 7:1093-1106). The physiological functions of BCMA, however,had not been determined prior to the present invention, and no one hadsuggested or identified a ligand for the receptor. The present inventorssought to determine whether BCMA was the receptor for TALL-1.

[0164] Initially, a soluble TALL-1 (sTALL-1) was produced in a humanembryonic kidney 293 cell line. Prior to this experiment, it had beenshown that the transmembrane TALL-1 precursor is cleaved between aminoacid residues R133 and A134 to form. sTALL-1 (Schneider et al., (1999),J. Exp. Med. 189:1747-1756). To produce sTALL-1, the present inventorsconstructed a mammalian secretion expression construct in which anN-terminal Flag epitope was fused in frame with a cDNA fragment encodingpositions 134-285 of the amino acid sequence of TALL-1 (positions134-285 of SEQ ID NO:2). Specifically, the cDNA fragment was amplifiedfrom a TALL-1 full-length cDNA clone⁶ by PCR with the following twoprimers: 5′-GGAAGCTTATGGACTACAAGGACGACGATG-3′ (SEQ ID NO:8) and5′-AAAGGATCCTACAGACATGGTGTAAGTAG-3′ (SEQ ID NO:9). The PCR product wasdigested with Hind III and BamHI, and inserted into the Hind III andBamHI sites of the pSec-Tag2B plasmid (Invitrogen, Carlsbad, Calif.) tomake pSec-Flag-sTALL-1. This construct was transiently or stablytransfected into 293 cells.

[0165] To detect Flag-sTALL-1 expression, 293 cells (3×10⁶/100 dish)were transfected with 10 μg of pSec-Flag-sTALL-1 or the empty controlpSec-TaqB2 plasmid by Ca³(PO⁴)₂ precipitation (Hu et al., (1999), J.Biol. Chem. 274:30603-30610; Shu et al., (1997), Immunity 6:751-763). 24hours after transfection, cell culture medium was collected. A 1 mlaliquot of the medium was incubated with 0.5 μg anti-Flag monoclonalantibody (Sigma, St. Luis, Mo.) (FIG. 5A; lanes 2 & 4) or 0.5 μg controlmouse IgG (FIG. 5A; lanes 1 & 3), and 25 μl of a 1:1 slurry of GammaBindG Plus Sepharose (Pharmacia, Uppsala, Sweden) at 4° C. for 3 hours. Thesepharose beads were washed three times with 1 ml lysis buffer. Theprecipitates were fractionated on SDS-PAGE and western blot analysis wasperformed with the anti-Flag antibody (Sigma). Western blots wereperformed as described (Hu et al., 1999; Shu et al., 1997). FIG. 5Aconfirms that Flag-tagged sTALL-1 (Flag-sTALL-1) was expressed in theculture medium.

[0166] The secreted Flag-sTALL-1 was also purified with an anti-Flagantibody affinity column (FIG. 5B). To purify Flag-sTALL-1, 500 ml ofconditioned medium from the 293 stable cell line expressing Flag-sTALL-1was collected and supplemented with 10 mM Tris (pH 7.5) and 100 mM NaCl.2 ml of anti-Flag antibody affinity chromatography column (Sigma, St.Luis, Mo.) was pre-washed with three sequential 5 ml of aliquots of 0.1M glycine (pH 3.5) and followed by three sequential 5 ml of TBS buffer(50 mM Tris, 150 mM NaCl, pH 7.4). The medium was passed through thecolumn and the column was washed with 12 ml aliquots of TBS for threetimes. The proteins bound to the column were eluted with 100 μg/ml Flagpeptide (Sigma, St. Luis, Mo.) and analyzed by Coomassie blue staining(FIG. 5B; left lane) or Western blot with anti-Flag antibody (FIG. 5B;right lane).

[0167] To determine whether TALL-1 binds to BCMA, the present inventorsnext constructed a mammalian expression construct for C-terminal HAepitope-tagged BCMA (BCMA-HA). To construct the mammalian expressionplasmid for C-terminal HA-tagged BCMA, a cDNA fragment encoding BCMA(SEQ ID NO:10) and a C-terminal HA epitope was amplified by PCR from anEST clone (GenBank Accession No. AA259026) with the following twoprimers:

[0168] 5′-ATAAGCTTTTTGTGATGATGTTG-3′ (SEQ ID NO:12); and,

[0169] 5′-TTGGATCCTTAAGCGTAATCTGGAACATCGTATGGGTACCTAGCAGAAATTGAT-3′ (SEQID NO:13).

[0170] The amplified cDNA fragment was digested with Hind III and BamH Iand cloned into the Hind III and BamH I site of a CMV promoter basedplasmid to make pCMV-BCMA-HA.

[0171] To detect interaction between Flag-sTALL-1 and BCMA-HA, 293 cells(3×10⁶/100 mm dish) were transfected with 10 μg of the expressionplasmid for BCMA-HA (FIG. 6A; lanes 1-4,7,8) or an empty control plasmid(FIG. 6A; lanes 5 & 6). 24 hours after transfection, cells were lysed in1.0 ml lysis buffer (20 mM Tris [pH 7.5], 150 mM NaCl, 1% Triton, 1 mMEDTA, 10 μg/ml aprotinin, 10 μg/ml leupeptin, 1 mM PMSF). The lysateswere mixed with 5 ml of control conditioned medium (FIG. 6A; lanes 1&2;cell culture medium from the empty pSec-TagB2 plasmid transfected 293cells), Flag-sTALL-1 containing medium (FIG. 6A; lanes 3-6), or controlconditioned medium plus 0.1 μg recombinant Flag-sTRAIL (provided by Dr.Bryant Barnay) (FIG. 6A; lanes 7 & 8). The mixtures were split into 2aliquots and each aliquot was incubated with 0.5 μg anti-HA monoclonalantibody (BABCO, Berkeley, Calif.) (FIG. 6A; lanes 2,4,6,8) or controlmouse IgG (FIG. 6A; lanes 1, 3, 5, 7), and 25 μl of a 1:1 slurry ofGammaBind G Plus Sepharose at 4° C. for 3 hours. The sepharose beadswere washed three times with 1 ml lysis buffer containing 500 mM NaCl.The precipitates were analyzed by Western blot with anti-Flag antibody(FIG. 6A; upper panel). The same blot was stripped and reprobed withanti-HA antibody (FIG. 6A; lower panel). All conditioned medium wassupplemented with 10 mM Tris (pH 7.5), 100 mM NaCl, 1 mM EDTA, 10 μg/mlaprotinin, 10 μg/ml leupeptin, and 1 mM PMSF before THimmunoprecipitation experiments. Western blots were performed asdescribed above. As shown in FIG. 6A, co-immunoprecipitation and Westernblot analysis indicated that BCMA-HA interacted with Flag-sTALL-1.BCMA-HA did not interact with proteins in control medium or Flag-taggedsoluble TRAIL (Flag-sTRAIL) (FIG. 6A), another member of the TNF family(Nataga, (1997), Cell 88:355-365; Ashkenazi et al., (1999), Curr. Opin.Cell Biol. 11:255-260). The higher molecular weight band in FIG. 6A isprobably a glycosylated form of BCMA, which has been shown to be aglycoprotein (Gras et al., (1995), International Immunology7:1093-1106).

[0172] To determine whether the binding of TALL-1 to BCMA is specific orwhether TALL-1 non-specifically binds to any member of the TNF receptorfamily, the present inventors next examined whether Flag-sTALL-1interacts with TRAIL-R1/DR4 and TRAIL-R2/DR5, two receptors for TRAIL(Pan et al., (1997), Science 276:111-113; Pan et al., (1997), Science277:815-817). To do this, conditioned medium containingFlag-sTRAIL-R1-Fc (Pan et al., (1997), Science 276:111-113) orFlag-sTRAIL-R2-Fc (Pan et al., (1997), Science 277:815-817) fusionprotein was mixed with conditioned medium containing Flag-sTALL-1 orFlag-sTRAIL. The expression plasmids for Flag-sTRAIL-RI-Fc andFlag-sTRAIL-R2-Fc were provided by Dr. Claudio Vincenz. The productionof these constructs is described in Pan et al., 1997, “The receptor forthe cytotoxic ligand TRAIL”, Science 276:111-113; and in Pan et al.,1997, “An antagonist decoy receptor and a death domain-containingreceptor for TRAIL”, Science 277:815-817; both of which are incorporatedherein by reference in their entireties.

[0173] To detect the interaction between Flag-sTALL-1 or Flag-sTRAIL andFlag-TRAIL-R1-Fc or Flag-TRAIL-R2-Fc, 293 cells (3×10⁶/100 dish) weretransfected with 10 μg of the mammalian secretion expression plasmid forFlag-sTRAIL-R1-Fc, Flag-sTRAIL-R2-Fc, or Flag-Fc control. Cell culturemedium was collected 24 hours after transfection. 3 ml aliquot of themedium was mixed with 3 ml of Flag-sTALL-1 (FIG. 6B; lanes 1-3) orFlag-sTRAIL (FIG. 6B; lanes 4-6) containing medium. The mixture wasincubated with 25 μl of a 1:1 slurry of GammaBind G Plus Sepharose at 4°C. for 3 hours. The beads were washed with the lysis buffer three times.The precipitates were analyzed by Western blot with anti-Flag antibodyas described above. As above, all conditioned medium was supplementedwith 10 mM Tris (pH 7.5), 100 mM NaCl, 1 mM EDTA, 10 μg/ml aprotinin, 10μg/ml leupeptin, and 1 mM PMSF before TH immunoprecipitationexperiments. As shown in FIG. 6B, Flag-sTALL-1 does not interact withTRAIL-R1 and TRAIL-R2. As expected, Flag-sTRAIL interacted with TRAIL-R1and TRAIL-R2 in the same experiment (FIG. 6B). Taken together, theseexperiments suggest that TALL-1 specifically (i.e., selectively)interacts with BCMA.

Example 3

[0174] The following example demonstrates that BCMA can be targeted tothe plasma membrane where it can bind to sTALL-1.

[0175] Although it has been experimentally demonstrated that BCMA caninsert into canine microsomes as a glycosylated type I integral membraneprotein in vitro (Gras et al., (1995), International Immunology7:1093-1106), immunocytochemistry and subfractionation studies indicatedthat BCMA was enriched in Golgi apparatus and failed to detect BCMA onthe plasma membrane (Gras et al., 1995, ibid.). In addition, sequenceanalysis suggests that BCMA has no recognizable signal peptide at itsN-terminus (Laabi et al., (1992), EMBO J. 11:3897-3904; Laabi et al.,(1994), Nucleic Acids Research 22:1147-1154; Gras et al., (1995),International Immunology 7:1093-1106). These observations raise thequestion of whether BCMA can function as a plasma membrane-boundreceptor. To resolve this question, the present inventors performed flowcytometry analysis. To do this, we first tested whether the Flag-sTALL-1protein produced by the present inventors could bind to its receptor onthe plasma membrane of the B lymphocyte-derived Bjab cell line, whichhas been shown to express the previously unidentified TALL-1 receptor(Schneider et al., 1999). For most flow cytometry experiments describedin this example, cells (1×10⁶) were incubated with 500 μl control medium(from the empty control pSec-TagB2 plasmid transfected 293 cells) (FIG.7A; shaded histograms) or with Flag-sTALL-1 containing medium (FIG. 7A;solid line histograms) for 40 minutes. Cell staining was performed bysequential incubation (each 40 minutes) with anti-Flag monoclonalantibody (1 μg/ml) and RPE-conjugated goat anti-mouse IgG (1:200dilution) in staining buffer (D-PBS containing 2% fetal bovine serum).Cells were washed two times with staining buffer following eachincubation. The fluorescence exhibited by the stained cells was measuredusing a Becton Dickenson FACScan flow cytometer.

[0176] As shown in FIG. 7A, flow cytometry analysis indicates thatFlag-sTALL-1 can bind to the plasma membrane of Bjab cells, but not ofthe monocytic U937 cells, the T lymphoma Jurkat cells, or the embryonickidney 293 cells. These data suggest that Bjab, but not U937, Jurkat or293 cells, express the TALL-1 receptor.

[0177] To test whether BCMA can function as a membrane receptor, 293cells were transfected with the expression plasmid for BCMA, describedin Example 2 above. As controls, 293 cells were also transfected withempty control plasmid (described above), with CD40 (provided by Dr.David Goeddel) or with TNF-R2 (provided by Dr. David Goeddel). 24 hoursafter transfection, cells were incubated with control medium (shadedhistogram) or Flag-sTALL-1 containing medium (solid line histogram), andflow cytometry analysis of the transfected intact cells was performedwith anti-Flag antibody as described above.

[0178] As shown in FIG. 7B, Flag-sTALL-1 could bind to the plasmamembrane of BCMA transfected cells, but not to cells transfected withthe empty control plasmid, with CD40 or with TNF-R2 transfected cells.These data indicate that BCMA can be targeted to the plasma membrane,and that sTALL-1 specifically binds to the plasma membrane-bound BCMAbut not to other examined TNF receptor family members. It is noted thatsome well established TNF receptor family members, such as human TNF-R1,TRAIL-R4 (Degli-Esposti et al., (1997), Immunity 7:813-820), and HVEM(Montgomery et al., (1996), Cell 87:427-436) also do not have arecognizable signal peptide based on structural analysis with existingsoftware programs (data not shown). In addition, many examined TNFreceptor family members, such as TNF-R1 and Fas, are found to beenriched in the Golgi apparatus and not or barely detectable on plasmamembrane by immunocytochemistry and subfractionation experiments(Bennett et al., (1998), Science 282:290-293; Jones et al., (1999), J.Immunol. 162:1042-1048; Cottin et al., (1999), J. Biol. Chem.274:32975-32987). However, flow cytometry analysis, a more sensitivemethod, could easily detect TNF-R1 and Fas on plasma membrane in thesame cell types (Bennett et al., (1998), Science 282:290-293; Jones etal., (1999), J. Immunol. 162:1042-1048). This is the first demonstrationthat BCMA shares this feature with other TNF receptor family members.

Example 4

[0179] The following example demonstrates that soluble BCMA inhibitsTALL-1 binding to Bjab cells and inhibits TALL-1-triggered B lymphocyteproliferation.

[0180] To determine whether TALL-1 signals through BCMA, the presentinventors next investigated whether soluble BCMA (sBCMA) could block thebinding of TALL-1 to its receptor on Bjab cells and whether sBCMA couldinhibit TALL-1-triggered B lymphocyte proliferation. To determinewhether soluble BCMA (sBCMA) could block the binding of TALL-1 to itsreceptor, a secreted fusion protein Flag-sBCMA-Fc, which consisted of anN-terminal Flag tag, the extracellular domain of BCMA (amino acidpositions 1-62 of SEQ ID NO:11) and the Fe fragment of immunoglobulin GI(IgG1) was produced. Specifically, to construct a mammalian secretionexpression plasmid for soluble BCMA and Fe fusion protein, a cDNAencoding amino acid positions 1-62 of human BCMA (SEQ ID NO:11) wasamplified by PCR from the EST clone AA259026 (described above) with thefollowing two primers: 5′-GGGAATTCCATGTTGCAGATGGCTG-3′ (SEQ ID NO:14)and 5′-GGGGATCCAAA CAGGTCCAGAG-3′ (SEQ ID NO:15). The PCR product wasdigested with EcoR I and BamH I and inserted into the EcoR I and Bgl IIsites of the pCMV1-Flag-Fc plasmid (Pan et al., (1997), Science276:111-113)to make pCMV1-Flag-sBCMA-Fc. To produce soluble BCMA for usein the experiment, 293 cells (3×10⁶/100 mm dish) were transfected with10 μg of pCMV1-Flag-sBCMA-Fc plasmid. 12 hours later, cells were washedwith PBS and fresh medium was added. 36 hours after that, cell culturemedium was collected and concentrated for 50 folds by centrifugationwith Centricon-30 (Millipore, Bedford, Mass.).

[0181] Bjab cells were incubated with 500 μl control medium (FIG. 7C,shaded histogram), 250 μl Flag-sTALL-1 containing medium plus 250 μlcontrol medium (FIG. 7C, solid line histogram), or 250 μl Flag-sTALL-lmedium plus 250 μl concentrated Flag-sBCMA-Fc containing medium (FIG.7C, dashed line histogram). As described in Examples 2 and 3, cellstaining was performed by sequential incubation (each 40 minutes) withanti-Flag monoclonal antibody (1 μg/ml) and RPE-conjugated goatanti-mouse IgG (1:200 dilution) in staining buffer (D-PBS containing 2%fetal bovine serum). Cells were washed two times with staining bufferfollowing each incubation. The fluorescence exhibited by the stainedcells was measured using a Becton Dickson FACScan flow cytometer. Asshown in FIG. 7C, this experiment demonstrated that Flag-sBCMA-Fcpartially blocked sTALL-1 binding to its receptor on Bjab cells.

[0182] To determine whether sBCMA could inhibit TALL-1-triggered Blymphocyte proliferation, human peripheral B lymphocytes were purifiedfrom peripheral blood of health donors using anti-CD19 dynal beads andDETACHaBEADanti-CD19 (Dynal Inc., Lake Success, N.Y.) followingprocedures suggested by the manufacture. Purified B lymphocytes (1×10⁵)were seeded on 96-well dishes and treated with the following reagentsfor 40 hours: 1. TBS control buffer; 2. Flag-sTALL-1 (100 ng/ml); 3.Anti-IgM (10 μg/ml); 4. Flag-sTALL-1 (100 ng/ml)+anti-IgM (10 μg/ml); 5.Flag-sTALL-1 (100 ng/ml)+anti-IgM (10 μg/ml)+concentrated Flag-sBCMA-Fc(5 μl); 6. Flag-sTALL-1 (100 ng/ml)+anti-IgM (10 μg/ml)+concentratedFlag-Fc (5 μl). Cells were then pulsed for an additional 10 hours with[³H]-thymidine (1 μCi/well) (NEN Life Biotechnology, Boston, Mass.).Incorporation of [³H]-thymidine was measured by liquid scintillationcounting. The data shown in FIG. 8 are averages and standard deviationsof one representative experiment in which each treatment had beenperformed in triplicate. FIG. 8 demonstrates that Flag-sBCMA-Fc, but notFlag-Fc, significantly (p<0.01) inhibited sTALL-1-triggered B lymphocyteproliferation. These data are consistent with the conclusion that TALL-1signals through BCMA.

Example 5

[0183] The following example demonstrates that BCMA activates NF-κB andthis activation is potentiated by sTALL-1.

[0184] Many members of the TNF receptor family can activate NF-κB whenoverexpressed in mammalian cells (Baker and Reddy, 1998; Rothe et al.,1995; Hu et al., 1999). To determine whether BCMA can also activateNF-κB, 293 cells were transfected with a mammalian expression plasmidfor BCMA as described above (i.e., the BCMA-HA plasmid). Briefly, 293cells were transfected with 0.5 μg of NF-κB luciferase reporter plasmidand increased amounts of an expression plasmid for BCMA. 14 hours aftertransfection, cells were treated with 100 ng/ml Flag-sTALL-1 (FIG. 9,black bars) or were left untreated (FIG. 9, white bars) for 7 hours andluciferase reporter assays were performed. The luciferase reporter geneassays were performed as described (Smith et al., (1994), Cell76:959-963; Wong et al., (1997), J. Biol. Chem. 272:25190-25195). Withinthe same experiment, each transfection was performed in triplicate, andwhere necessary, enough of the empty control plasmid was added so thateach transfection received the same amount of total DNA. To normalizefor transfection efficiency and protein amount, 0.5 μg of RSV-β-galplasmid was added to all transfections. Luciferase activities werenormalized on the basis of β-galactosidase expression levels. Data shownin FIG. 9 are averages and standard deviations of one representativeexperiment in which each transfection had been performed in triplicate.

[0185] The luciferase reporter gene assays indicated that transfectionof BCMA activated NF-κB in a dose dependent manner in 293 cells (FIG.9). Transfection of BCMA did not activate an interferon response factorin reporter gene assays (data not shown), suggesting that BCMA-mediatedNF-κB activation is not due to non-specific activation of transcriptionand/or translation. Moreover, sTALL-1 stimulation potentiatedBCMA-mediated NF-κB activation very well, especially when BCMA wasexpressed at low levels (FIG. 9). When BCMA was expressed at highlevels, sTALL-1 stimulation could only weakly potentiate BCMA-mediatedNF-κB activation. Two phenomena may account for this. First, it has beenwidely accepted that activation of TNF receptor family members istriggered by ligand-mediated oligomerization of the receptors. When thereceptors are expressed at high levels, they may achieve maximumself-oligomerization even without their ligands. Secondly, at highexpression levels of BCMA, downstream NF-κB activation signaling may besaturated. Taken together, these data suggest BCMA can activate NF-κBand that TALL-1 can signal through BCMA.

Example 6

[0186] The following example demonstrates that TRAF5, TRAF6, NIK, andIKKs are involved in BCMA-mediated NF-κB activation.

[0187] Previously, it had been shown that intracellular signalingproteins TRADD, TRAF2, TRAF5, TRAF6, RIP, NIK, IKKα, and IKKβ areinvolved in NF-κB activation pathways mediated by several TNF receptorfamily members (Nataga, (1997), Cell 88:355-365; Baker et al., (1998),Oncogene 17:3261-3270; Rothe et al., (1995), Science 269:1424-1427; Huet al., (1999), J. Biol. Chem. 274:30603-30610). The present inventorsexamined whether these proteins are also involved in NF-κB activation byBCMA. Dominant negative mutants of TRADD, TRAF2, TRAF5, TRAF6, RIP, NIK,IKKα, and IKKβ were obtained for use in the assay as follows:TRADD(296S), Flag-TRAF2(87-501), Myc-RIP (559-671), Myc-NIK(KK/AA),Flag-IKKα(K44A), and Flag-IKKβ(K44A) were all provided by Dr. DavidGoeddel; Flag-TRAF6(289-523) was provided by Dr. Zhaodan Cao; and themammalian expression plasmid for TRAF5 dominant negative mutant wasconstructed by insertion of a PCR product encoding amino acids 69-557 ofhuman TRAF5 into the pRK-Flag vector (Hu et al., (1999), J. Biol. Chem.274:30603-30610; Shu et al., (1997), Immunity 6:751-763). It is notedthat details regarding the construction of the above-identifiedconstructs provided by Dr. Goeddel or Dr. Cao are published as follows:TRADD(296S): (Park et al., 1996, J. Biol. Chem. 271, 9858-9862;Flag-TRAF2(87-501): Rothe et al., 1995, Science 269, 1424-1427;Myc-RIP(559-671): Hsu et al., 1996b, Immunity 4, 387-396;Myc-NIK(KK/AA): Song et al., 1997, Proc. Natl. Acad. Sci. U.S.A. 94,9792-9796; Flag-IKKα: Regnier et al., 1997, Cell 90,373-383; Flag-IKKβ:Woronicz et al., 1997, Science 278, 866-869; and, Flag-TRAF6(289-523):Cao et al., 1996, Nature 383, 443-446. Each of the above-identifiedpublications is incorporated in its entirety by reference.

[0188] In the first portion of the experiment (See FIG. 10A), 293 cellswere transfected with 0.5 μg of NF-κB reporter plasmid (described inExample 4), 0.5 μg of BCMA-HA expression plasmid (described in Example2), and 1 μg of control plasmid or expression plasmids for the dominantnegative mutants indicated in FIG. 10A. 0.5 μg of crmA plasmid was alsoadded to the Myc-RIP(559-671) transfections for inhibiting apoptosis. 20hours after transfection, luciferase assays were performed as describedin Example 4, and data were treated as described in Example 4.Expression of the HA-tagged BCMA and the Flag- or Myc-tagged mutantswere examined by Western blots with antibodies against the HA, Flag, orMyc epitopes, respectively. TRADD(296S) and IκBα(SS/AA) (a mammalianexpression plasmid for mutated Inhibitory κB, having amino acids S32 andS36 mutated to A32 and A36) are not tagged and could not be detected inthe Western blot portion of the experiment (FIG. 10A, lower section). Asshown in FIG. 10A (upper and lower sections), dominant negative mutantsof TRAF5, TRAF6, NIK, IKKα and IKKβ, but not of TRADD, TRAF2, and RIP,inhibited BCMA-mediated NF-κB activation.

[0189] In the second portion of the experiment (See FIG. 10B), 293 cellswere transfected with expression plasmids for HA-BCMA and the plasmidsindicated in FIG. 10B. Transfected cell lysates were immunoprecipitatedwith anti-Flag antibody or control IgG. The immunoprecipitates wereanalyzed by Western blot with anti-HA antibody (FIG. 10B; upper panel).Expression of the transfected proteins were detected by Western blotswith anti-Flag (FIG. 10B; middle panel) or anti-HA antibody (FIG. 10B;lower panel). Consistent with the results demonstrated in FIG. 10A, thepresent inventors found that BCMA physically interacted with TRAF5 andTRAF6, but not TRAF2, TRADD or RIP in these co-immunoprecipitationexperiments (FIG. 10B).

[0190] Taken together, these data suggest that TRAF5, TRAF6, NIK, IKKαand IKKβ, but not TRAF2, TRADD and RIP, are involved in BCMA-mediatedNF-κB activation pathways. In conclusion, the data in Examples 2-5suggest that BCMA is a B lymphocyte specific receptor for TALL-1 andthat BCMA activates NF-κB through pathways involved in TRAF5, TRAF6,NIK, IKKα and IKKβ. The constitutive expression of TALL-1 bymonocytes/macrophages and the specific expression of its receptor BCMAby B lymphocytes indicates that peripheral B lymphocyte proliferation,survival and activation are critically regulated by monocytes andrelated cells through secretion of sTALL-1. Manipulation of theTALL-1/BCMA signaling system is expected to provide novel approaches formodulation of B cell-mediated immune responses and diseases.

[0191] While various embodiments of the present invention have beendescribed in detail, it is apparent that modifications and adaptationsof those embodiments will occur to those skilled in the art. It is to beexpressly understood, however, that such modifications and adaptationsare within the scope of the present invention, as set forth in thefollowing claims:

1 17 1 855 DNA Artificial Sequence CDS (1)..(855) Description ofArtificial Sequenceprimer 1 atg gat gac tcc aca gaa agg gag cag tca cgcctt act tct tgc ctt 48 Met Asp Asp Ser Thr Glu Arg Glu Gln Ser Arg LeuThr Ser Cys Leu 1 5 10 15 aag aaa aga gaa gaa atg aaa ctg aag gag tgtgtt tcc atc ctc cca 96 Lys Lys Arg Glu Glu Met Lys Leu Lys Glu Cys ValSer Ile Leu Pro 20 25 30 cgg aag gaa agc ccc tct gtc cga tcc tcc aaa gacgga aag ctg ctg 144 Arg Lys Glu Ser Pro Ser Val Arg Ser Ser Lys Asp GlyLys Leu Leu 35 40 45 gct gca acc ttg ctg ctg gca ctg ctg tct tgc tgc ctcacg gtg gtg 192 Ala Ala Thr Leu Leu Leu Ala Leu Leu Ser Cys Cys Leu ThrVal Val 50 55 60 tct ttc tac cag gtg gcc gcc ctg caa ggg gac ctg gcc agcctc cgg 240 Ser Phe Tyr Gln Val Ala Ala Leu Gln Gly Asp Leu Ala Ser LeuArg 65 70 75 80 gca gag ctg cag ggc cac cac gcg gag aag ctg cca gca ggagca gga 288 Ala Glu Leu Gln Gly His His Ala Glu Lys Leu Pro Ala Gly AlaGly 85 90 95 gcc ccc aag gcc ggc ttg gag gaa gct cca gct gtc acc gcg ggactg 336 Ala Pro Lys Ala Gly Leu Glu Glu Ala Pro Ala Val Thr Ala Gly Leu100 105 110 aaa atc ttt gaa cca cca gct cca gga gaa ggc aac tcc agt cagaac 384 Lys Ile Phe Glu Pro Pro Ala Pro Gly Glu Gly Asn Ser Ser Gln Asn115 120 125 agc aga aat aag cgt gcc gtt cag ggt cca gaa gaa aca gtc actcaa 432 Ser Arg Asn Lys Arg Ala Val Gln Gly Pro Glu Glu Thr Val Thr Gln130 135 140 gac tgc ttg caa ctg att gca gac agt gaa aca cca act ata caaaaa 480 Asp Cys Leu Gln Leu Ile Ala Asp Ser Glu Thr Pro Thr Ile Gln Lys145 150 155 160 gga tct tac aca ttt gtt cca tgg ctt ctc agc ttt aaa agggga agt 528 Gly Ser Tyr Thr Phe Val Pro Trp Leu Leu Ser Phe Lys Arg GlySer 165 170 175 gcc cta gaa gaa aaa gag aat aaa ata ttg gtc aaa gaa actggt tac 576 Ala Leu Glu Glu Lys Glu Asn Lys Ile Leu Val Lys Glu Thr GlyTyr 180 185 190 ttt ttt ata tat ggt cag gtt tta tat act gat aag acc tacgcc atg 624 Phe Phe Ile Tyr Gly Gln Val Leu Tyr Thr Asp Lys Thr Tyr AlaMet 195 200 205 gga cat cta att cag agg aag aag gtc cat gtc ttt ggg gatgaa ttg 672 Gly His Leu Ile Gln Arg Lys Lys Val His Val Phe Gly Asp GluLeu 210 215 220 agt ctg gtg act ttg ttt cga tgt att caa aat atg cct gaaaca cta 720 Ser Leu Val Thr Leu Phe Arg Cys Ile Gln Asn Met Pro Glu ThrLeu 225 230 235 240 ccc aat aat tcc tgc tat tca gct ggc att gca aaa ctggaa gaa gga 768 Pro Asn Asn Ser Cys Tyr Ser Ala Gly Ile Ala Lys Leu GluGlu Gly 245 250 255 gat gaa ctc caa ctt gca ata cca aga gaa aat gca caaata tca ctg 816 Asp Glu Leu Gln Leu Ala Ile Pro Arg Glu Asn Ala Gln IleSer Leu 260 265 270 gat gga gat gtc aca ttt ttt ggt gca ttg aaa ctg ctg855 Asp Gly Asp Val Thr Phe Phe Gly Ala Leu Lys Leu Leu 275 280 285 2285 PRT Artificial Sequence Description of Artificial Sequenceprimer 2Met Asp Asp Ser Thr Glu Arg Glu Gln Ser Arg Leu Thr Ser Cys Leu 1 5 1015 Lys Lys Arg Glu Glu Met Lys Leu Lys Glu Cys Val Ser Ile Leu Pro 20 2530 Arg Lys Glu Ser Pro Ser Val Arg Ser Ser Lys Asp Gly Lys Leu Leu 35 4045 Ala Ala Thr Leu Leu Leu Ala Leu Leu Ser Cys Cys Leu Thr Val Val 50 5560 Ser Phe Tyr Gln Val Ala Ala Leu Gln Gly Asp Leu Ala Ser Leu Arg 65 7075 80 Ala Glu Leu Gln Gly His His Ala Glu Lys Leu Pro Ala Gly Ala Gly 8590 95 Ala Pro Lys Ala Gly Leu Glu Glu Ala Pro Ala Val Thr Ala Gly Leu100 105 110 Lys Ile Phe Glu Pro Pro Ala Pro Gly Glu Gly Asn Ser Ser GlnAsn 115 120 125 Ser Arg Asn Lys Arg Ala Val Gln Gly Pro Glu Glu Thr ValThr Gln 130 135 140 Asp Cys Leu Gln Leu Ile Ala Asp Ser Glu Thr Pro ThrIle Gln Lys 145 150 155 160 Gly Ser Tyr Thr Phe Val Pro Trp Leu Leu SerPhe Lys Arg Gly Ser 165 170 175 Ala Leu Glu Glu Lys Glu Asn Lys Ile LeuVal Lys Glu Thr Gly Tyr 180 185 190 Phe Phe Ile Tyr Gly Gln Val Leu TyrThr Asp Lys Thr Tyr Ala Met 195 200 205 Gly His Leu Ile Gln Arg Lys LysVal His Val Phe Gly Asp Glu Leu 210 215 220 Ser Leu Val Thr Leu Phe ArgCys Ile Gln Asn Met Pro Glu Thr Leu 225 230 235 240 Pro Asn Asn Ser CysTyr Ser Ala Gly Ile Ala Lys Leu Glu Glu Gly 245 250 255 Asp Glu Leu GlnLeu Ala Ile Pro Arg Glu Asn Ala Gln Ile Ser Leu 260 265 270 Asp Gly AspVal Thr Phe Phe Gly Ala Leu Lys Leu Leu 275 280 285 3 250 PRT Homosapiens 3 Met Pro Ala Ser Ser Pro Phe Leu Leu Ala Pro Lys Gly Pro ProGly 1 5 10 15 Asn Met Gly Gly Pro Val Arg Glu Pro Ala Leu Ser Val AlaLeu Trp 20 25 30 Leu Ser Trp Gly Ala Ala Leu Gly Ala Val Ala Cys Ala MetAla Leu 35 40 45 Leu Thr Gln Gln Thr Glu Leu Gln Ser Leu Arg Arg Glu ValSer Arg 50 55 60 Leu Gln Gly Thr Gly Gly Pro Ser Gln Asn Gly Glu Gly TyrPro Trp 65 70 75 80 Gln Ser Leu Pro Glu Gln Ser Ser Asp Ala Leu Glu AlaTrp Glu Asn 85 90 95 Gly Glu Arg Ser Arg Lys Arg Arg Ala Val Leu Thr GlnLys Gln Lys 100 105 110 Lys Gln His Ser Val Leu His Leu Val Pro Ile AsnAla Thr Ser Lys 115 120 125 Asp Asp Ser Asp Val Thr Glu Val Met Trp GlnPro Ala Leu Arg Arg 130 135 140 Gly Arg Gly Leu Gln Ala Gln Gly Tyr GlyVal Arg Ile Gln Asp Ala 145 150 155 160 Gly Val Tyr Leu Leu Tyr Ser GlnVal Leu Phe Gln Asp Val Thr Phe 165 170 175 Thr Met Gly Gln Val Val SerArg Glu Gly Gln Gly Arg Gln Glu Thr 180 185 190 Leu Phe Arg Cys Ile ArgSer Met Pro Ser His Pro Asp Arg Ala Tyr 195 200 205 Asn Ser Cys Tyr SerAla Gly Val Phe His Leu His Gln Gly Asp Ile 210 215 220 Leu Ser Val IleIle Pro Arg Ala Arg Ala Lys Leu Asn Leu Ser Pro 225 230 235 240 His GlyThr Phe Leu Gly Phe Val Lys Leu 245 250 4 147 PRT Homo sapiens 4 Lys ProVal Ala His Val Val Ala Asn Pro Gln Ala Glu Gly Gln Leu 1 5 10 15 GlnTrp Leu Asn Arg Arg Ala Asn Ala Leu Leu Ala Asn Gly Val Glu 20 25 30 LeuArg Asp Asn Gln Leu Val Val Pro Ser Glu Gly Leu Tyr Leu Ile 35 40 45 TyrSer Gln Val Leu Phe Lys Gly Gln Gly Cys Pro Ser Thr His Val 50 55 60 LeuLeu Thr His Thr Ile Ser Arg Ile Ala Val Ser Tyr Gln Thr Lys 65 70 75 80Val Asn Leu Leu Ser Ala Ile Lys Ser Pro Cys Gln Arg Glu Thr Pro 85 90 95Glu Gly Ala Glu Ala Lys Pro Trp Tyr Glu Pro Ile Tyr Leu Gly Gly 100 105110 Val Phe Gln Leu Glu Lys Gly Asp Arg Leu Ser Ala Glu Ile Asn Arg 115120 125 Pro Asp Tyr Leu Asp Phe Ala Glu Ser Gly Gln Val Tyr Phe Gly Ile130 135 140 Ile Ala Leu 145 5 138 PRT Homo sapiens 5 Arg Lys Val Ala HisLeu Thr Gly Lys Ser Asn Ser Arg Ser Met Pro 1 5 10 15 Leu Glu Trp GluAsp Thr Tyr Gly Ile Val Leu Leu Ser Gly Val Lys 20 25 30 Tyr Lys Lys GlyGly Leu Val Ile Asn Glu Thr Gly Leu Tyr Phe Val 35 40 45 Tyr Ser Lys ValTyr Phe Arg Gly Gln Ser Cys Asn Asn Leu Pro Leu 50 55 60 Ser His Lys ValTyr Met Arg Asn Ser Lys Tyr Pro Gln Asp Leu Val 65 70 75 80 Met Met GluGly Lys Met Met Ser Tyr Cys Thr Thr Gly Gln Met Trp 85 90 95 Ala Arg SerSer Tyr Leu Gly Ala Val Phe Asn Leu Thr Ser Ala Asp 100 105 110 His LeuTyr Val Asn Val Ser Glu Leu Ser Leu Val Asn Phe Glu Glu 115 120 125 SerGln Thr Phe Phe Gly Leu Tyr Lys Leu 130 135 6 144 PRT Homo sapiens 6 LysPro Ala Ala His Leu Ile Gly Asp Pro Ser Lys Gln Asn Ser Leu 1 5 10 15Leu Trp Arg Ala Asn Thr Asp Arg Ala Phe Leu Gln Asp Gly Phe Ser 20 25 30Leu Ser Asn Asn Ser Leu Leu Val Pro Thr Ser Gly Ile Tyr Phe Val 35 40 45Tyr Ser Gln Val Val Phe Ser Gly Lys Ala Tyr Ser Pro Lys Ala Thr 50 55 60Ser Ser Pro Leu Tyr Leu Ala His Glu Val Gln Leu Phe Ser Ser Gln 65 70 7580 Tyr Pro Phe His Val Pro Leu Leu Ser Ser Gln Lys Met Val Tyr Pro 85 9095 Gly Leu Gln Glu Pro Trp Leu His Ser Met Tyr His Gly Ala Ala Phe 100105 110 Gln Leu Thr Gln Gly Asp Gln Leu Ser Thr His Thr Asp Gly Ile Pro115 120 125 His Leu Val Leu Ser Pro Ser Thr Val Phe Phe Gly Ala Phe AlaLeu 130 135 140 7 161 PRT Homo sapiens 7 Arg Val Ala Ala His Ile Thr GlyThr Arg Gly Arg Ser Asn Thr Leu 1 5 10 15 Ser Ser Pro Asn Ser Lys AsnGlu Lys Ala Leu Gly Arg Lys Ile Asn 20 25 30 Ser Trp Glu Ser Ser Arg SerGly His Ser Phe Leu Ser Asn Leu His 35 40 45 Leu Arg Asn Gly Glu Leu ValIle His Glu Lys Gly Phe Tyr Tyr Ile 50 55 60 Tyr Ser Gln Thr Tyr Phe ArgPhe Gln Glu Glu Ile Lys Glu Asn Thr 65 70 75 80 Lys Asn Asp Lys Gln MetVal Gln Tyr Ile Tyr Lys Tyr Thr Ser Tyr 85 90 95 Pro Asp Pro Ile Leu LeuMet Lys Ser Ala Arg Asn Ser Cys Trp Ser 100 105 110 Lys Asp Ala Glu TyrGly Leu Tyr Ser Ile Tyr Gln Gly Gly Ile Phe 115 120 125 Glu Leu Lys GluAsn Asp Arg Ile Phe Val Ser Val Thr Asn Glu His 130 135 140 Leu Ile AspMet Asp His Glu Ala Ser Phe Phe Gly Ala Phe Leu Val 145 150 155 160 Gly8 30 DNA Artificial Sequence Description of Artificial Sequenceprimer 8ggaagcttat ggactacaag gacgacgatg 30 9 29 DNA Artificial SequenceDescription of Artificial Sequenceprimer 9 aaaggatcct acagacatggtgtaagtag 29 10 834 DNA Homo sapiens CDS (67)..(621) 10 ttgtaagatattacttgtcc ttccaggctg ttctttctgt agctcccttg ttttcttttt 60 gtgatc atg ttgcag atg gct ggg cag tgc tcc caa aat gaa tat ttt 108 Met Leu Gln Met AlaGly Gln Cys Ser Gln Asn Glu Tyr Phe 1 5 10 gac agt ttg ttg cat gct tgcata cct tgt caa ctt cga tgt tct tct 156 Asp Ser Leu Leu His Ala Cys IlePro Cys Gln Leu Arg Cys Ser Ser 15 20 25 30 aat act cct cct cta aca tgtcag cgt tat tgt aat gca agt gtg acc 204 Asn Thr Pro Pro Leu Thr Cys GlnArg Tyr Cys Asn Ala Ser Val Thr 35 40 45 aat tca gtg aaa gga acg aat gcgatt ctc tgg acc tgt ttg gga ctg 252 Asn Ser Val Lys Gly Thr Asn Ala IleLeu Trp Thr Cys Leu Gly Leu 50 55 60 agc tta ata att tct ttg gca gtt ttcgtg cta atg ttt ttg cta agg 300 Ser Leu Ile Ile Ser Leu Ala Val Phe ValLeu Met Phe Leu Leu Arg 65 70 75 aag ata agc tct gaa cca tta aag gac gagttt aaa aac aca gga tca 348 Lys Ile Ser Ser Glu Pro Leu Lys Asp Glu PheLys Asn Thr Gly Ser 80 85 90 ggt ctc ctg ggc atg gct aac att gac ctg gaaaag agc agg act ggt 396 Gly Leu Leu Gly Met Ala Asn Ile Asp Leu Glu LysSer Arg Thr Gly 95 100 105 110 gat gaa att att ctt ccg aga ggc ctc gagtac acg gtg gaa gaa tgc 444 Asp Glu Ile Ile Leu Pro Arg Gly Leu Glu TyrThr Val Glu Glu Cys 115 120 125 acc tgt gaa gac tgc atc aag agc aaa ccgaag gtc gac tct gac cat 492 Thr Cys Glu Asp Cys Ile Lys Ser Lys Pro LysVal Asp Ser Asp His 130 135 140 tgc ttt cca ctc cca gct atg gag gaa ggcgca acc att ctt gtc acc 540 Cys Phe Pro Leu Pro Ala Met Glu Glu Gly AlaThr Ile Leu Val Thr 145 150 155 acg aaa acg aat gac tat tgc aag agc ctgcca gct gct ttg agt gct 588 Thr Lys Thr Asn Asp Tyr Cys Lys Ser Leu ProAla Ala Leu Ser Ala 160 165 170 acg gag ata gag aaa tca att tct gct aggtaa ttaaccattt cgactcgagc 641 Thr Glu Ile Glu Lys Ser Ile Ser Ala Arg175 180 185 agtgccactt taaaaatctt ttgtcagaat agatgatgtg tcagatctctttaggatgac 701 tgtatttttc agttgccgat acagcttttt gtcctctaac tgtggaaactctttatgtta 761 gatatatttc tctaggttac tgttgggagc ttaatggtag aaacttccttggtttctatg 821 attaaagtct ttt 834 11 184 PRT Homo sapiens 11 Met Leu GlnMet Ala Gly Gln Cys Ser Gln Asn Glu Tyr Phe Asp Ser 1 5 10 15 Leu LeuHis Ala Cys Ile Pro Cys Gln Leu Arg Cys Ser Ser Asn Thr 20 25 30 Pro ProLeu Thr Cys Gln Arg Tyr Cys Asn Ala Ser Val Thr Asn Ser 35 40 45 Val LysGly Thr Asn Ala Ile Leu Trp Thr Cys Leu Gly Leu Ser Leu 50 55 60 Ile IleSer Leu Ala Val Phe Val Leu Met Phe Leu Leu Arg Lys Ile 65 70 75 80 SerSer Glu Pro Leu Lys Asp Glu Phe Lys Asn Thr Gly Ser Gly Leu 85 90 95 LeuGly Met Ala Asn Ile Asp Leu Glu Lys Ser Arg Thr Gly Asp Glu 100 105 110Ile Ile Leu Pro Arg Gly Leu Glu Tyr Thr Val Glu Glu Cys Thr Cys 115 120125 Glu Asp Cys Ile Lys Ser Lys Pro Lys Val Asp Ser Asp His Cys Phe 130135 140 Pro Leu Pro Ala Met Glu Glu Gly Ala Thr Ile Leu Val Thr Thr Lys145 150 155 160 Thr Asn Asp Tyr Cys Lys Ser Leu Pro Ala Ala Leu Ser AlaThr Glu 165 170 175 Ile Glu Lys Ser Ile Ser Ala Arg 180 12 23 DNAArtificial Sequence Description of Artificial Sequenceprimer 12ataagctttt tgtgatgatg ttg 23 13 54 DNA Artificial Sequence Descriptionof Artificial Sequenceprimer 13 ttggatcctt aagcgtaatc tggaacatcgtatgggtacc tagcagaaat tgat 54 14 25 DNA Artificial Sequence Descriptionof Artificial Sequenceprimer 14 gggaattcca tgttgcagat ggctg 25 15 22 DNAArtificial Sequence Description of Artificial Sequenceprimer 15ggggatccaa acaggtccag ag 22 16 558 DNA Mus musculus CDS (1)..(558) 16atg gcg caa cag tgt ttc cac agt gaa tat ttt gac agt ctg ctg cat 48 MetAla Gln Gln Cys Phe His Ser Glu Tyr Phe Asp Ser Leu Leu His 1 5 10 15gct tgc aaa ccg tgt cac ttg cga tgt tcc aac cct cct gca acc tgt 96 AlaCys Lys Pro Cys His Leu Arg Cys Ser Asn Pro Pro Ala Thr Cys 20 25 30 cagcct tac tgt gat cca agc gtg acc agt tca gtg aaa ggg acg tac 144 Gln ProTyr Cys Asp Pro Ser Val Thr Ser Ser Val Lys Gly Thr Tyr 35 40 45 acg gtgctc tgg atc ttc ttg ggg ctg acc ttg gtc ctc tct ttg gca 192 Thr Val LeuTrp Ile Phe Leu Gly Leu Thr Leu Val Leu Ser Leu Ala 50 55 60 ctt ttc acaatc tca ttc ttg ctg agg aag atg aac ccc gag gcc ctg 240 Leu Phe Thr IleSer Phe Leu Leu Arg Lys Met Asn Pro Glu Ala Leu 65 70 75 80 aag gac gagcct caa agc cca ggt cag ctt gac gga tcg gct cag ctg 288 Lys Asp Glu ProGln Ser Pro Gly Gln Leu Asp Gly Ser Ala Gln Leu 85 90 95 gac aag gcc gacacc gag ctg act agg atc agg gct ggt gac gac agg 336 Asp Lys Ala Asp ThrGlu Leu Thr Arg Ile Arg Ala Gly Asp Asp Arg 100 105 110 atc ttt ccc cgaagc ctg gag tat aca gtg gaa gag tgc acc tgt gag 384 Ile Phe Pro Arg SerLeu Glu Tyr Thr Val Glu Glu Cys Thr Cys Glu 115 120 125 gac tgt gtc aagagc aaa ccc aag ggg gat tct gac cat ttc ttc ccg 432 Asp Cys Val Lys SerLys Pro Lys Gly Asp Ser Asp His Phe Phe Pro 130 135 140 ctt cca gcc atggag gag ggg gca acc att ctt gtc acc aca aaa acg 480 Leu Pro Ala Met GluGlu Gly Ala Thr Ile Leu Val Thr Thr Lys Thr 145 150 155 160 ggt gac tacggc aag tca agt gtg cca act gct ttg caa agt gtc atg 528 Gly Asp Tyr GlyLys Ser Ser Val Pro Thr Ala Leu Gln Ser Val Met 165 170 175 ggg atg gagaag cca act cac act aga taa 558 Gly Met Glu Lys Pro Thr His Thr Arg 180185 17 185 PRT Mus musculus 17 Met Ala Gln Gln Cys Phe His Ser Glu TyrPhe Asp Ser Leu Leu His 1 5 10 15 Ala Cys Lys Pro Cys His Leu Arg CysSer Asn Pro Pro Ala Thr Cys 20 25 30 Gln Pro Tyr Cys Asp Pro Ser Val ThrSer Ser Val Lys Gly Thr Tyr 35 40 45 Thr Val Leu Trp Ile Phe Leu Gly LeuThr Leu Val Leu Ser Leu Ala 50 55 60 Leu Phe Thr Ile Ser Phe Leu Leu ArgLys Met Asn Pro Glu Ala Leu 65 70 75 80 Lys Asp Glu Pro Gln Ser Pro GlyGln Leu Asp Gly Ser Ala Gln Leu 85 90 95 Asp Lys Ala Asp Thr Glu Leu ThrArg Ile Arg Ala Gly Asp Asp Arg 100 105 110 Ile Phe Pro Arg Ser Leu GluTyr Thr Val Glu Glu Cys Thr Cys Glu 115 120 125 Asp Cys Val Lys Ser LysPro Lys Gly Asp Ser Asp His Phe Phe Pro 130 135 140 Leu Pro Ala Met GluGlu Gly Ala Thr Ile Leu Val Thr Thr Lys Thr 145 150 155 160 Gly Asp TyrGly Lys Ser Ser Val Pro Thr Ala Leu Gln Ser Val Met 165 170 175 Gly MetGlu Lys Pro Thr His Thr Arg 180 185

What is claimed is:
 1. An isolated TALL-1 protein.
 2. The isolatedprotein of claim 1, wherein said protein comprises an amino acidsequence selected from the group consisting of: a. SEQ ID NO:2; and, b.a homologue of SEQ ID NO:2, wherein said homologue comprises an aminoacid sequence selected from the group consisting of: (i) an amino acidsequence that is at least about 40% identical to SEQ ID NO:2 over atleast 175 amino acids of SEQ ID NO:2; and, (ii) an amino acid sequencethat is at least about 40% identical to SEQ ID NO:2 over positions134-285 of SEQ ID NO:2.
 3. The isolated protein of claim 1, wherein saidprotein comprises an amino acid sequence selected from the groupconsisting of: a. an amino acid sequence that is at least about 60%identical to SEQ ID NO:2 over at least 175 amino acids of SEQ ID NO:2;and, b. an amino acid sequence that is at least about 60% identical toSEQ ID NO:2 over positions 134-285 of SEQ ID NO:2.
 4. The isolatedprotein of claim 1, wherein said protein comprises an amino acidsequence selected from the group consisting of: a. an amino acidsequence that is at least about 80% identical to SEQ ID NO:2 over atleast 175 amino acids of SEQ ID NO:2; and, b. an amino acid sequencethat is at least about 80% identical to SEQ ID NO:2 over positions134-285 of SEQ ID NO:2.
 5. The isolated protein of claim 1, wherein saidprotein comprises an amino acid sequence selected from the groupconsisting of: a. an amino acid sequence that is at least about 90%identical to SEQ ID NO:2 over at least 175 amino acids of SEQ ID NO:2;and, b. an amino acid sequence that is at least about 90% identical toSEQ ID NO:2 over positions 134-285 of SEQ ID NO:2.
 6. The isolatedprotein of claim 1, wherein said protein comprises at least about 30contiguous amino acids of SEQ ID NO:2.
 7. The isolated protein of claim1, wherein said protein comprises at least about 50 contiguous aminoacids of SEQ ID NO:2.
 8. The isolated protein of claim 1, wherein saidprotein comprises at least about 130 contiguous amino acids of SEQ IDNO:2.
 9. The isolated protein of claim 1, wherein said protein comprisesamino acid residues 134 through 285 of SEQ ID NO:2.
 10. The isolatedprotein of claim 1, wherein said protein comprises an amino acidsequence represented by SEQ ID NO:2.
 11. The isolated protein of claim1, wherein said protein is encoded by a nucleic acid molecule comprisinga nucleic acid sequence that hybridizes under low stringency conditionsto the complement of a nucleic acid sequence represented by SEQ ID NO:1.12. The isolated protein of claim 1, wherein said protein is encoded bya nucleic acid molecule comprising a nucleic acid sequence thathybridizes under moderate stringency conditions to the complement of anucleic acid sequence represented by SEQ ID NO:1.
 13. The isolatedprotein of claim 1, wherein said protein is encoded by a nucleic acidmolecule comprising a nucleic acid sequence that hybridizes under highstringency conditions to the complement of a nucleic acid sequencerepresented by SEQ ID NO:1.
 14. The isolated protein of claim 1, whereinsaid protein is encoded by a nucleic acid molecule comprising a nucleicacid sequence represented by SEQ ID NO:1.
 15. The isolated protein ofclaim 1, wherein said protein is encoded by a nucleic acid moleculecomprising a nucleic acid sequence represented by nucleotide positions402 through 855 of SEQ ID NO:1.
 16. The isolated protein of claim 1,wherein said protein is soluble.
 17. The isolated protein of claim 1,wherein said protein has a biological activity selected from the groupconsisting of: (a) binding to a TALL-1 receptor; (b) costimulation of Blymphocyte proliferation; (c) costimulation of B lymphocyte activation;and (d) support of B lymphocyte survival.
 18. The isolated protein ofclaim 1, wherein said protein binds to a TALL-1 receptor.
 19. Theisolated protein of claim 1, wherein said homologue does not activate aTALL-1 receptor.
 20. An isolated antibody that specifically binds to theisolated protein of claim
 1. 21. An isolated nucleic acid moleculecomprising a nucleic acid sequence encoding a protein comprising anamino acid sequence selected from the group consisting of: a. SEQ IDNO:2; and, b. a homologue of SEQ ID NO:2, wherein said homologuecomprises an amino acid sequence selected from the group consisting of:(i) an amino acid sequence comprising at least 130 contiguous aminoacids of SEQ ID NO:2; and, (ii) an amino acid sequence comprising atleast positions 134-285 of SEQ ID NO:2.
 22. The isolated nucleic acidmolecule of claim 21, wherein said homologue comprises an amino acidsequence comprising at least 150 contiguous amino acids of SEQ ID NO:2.23. The isolated amino acid molecule of claim 21, wherein said homologuecomprises an amino acid sequence comprising at least 175 contiguousamino acids of SEQ ID NO:2.
 24. The isolated nucleic acid molecule ofclaim 21, wherein said nucleic acid sequence encodes a proteincomprising an amino acid sequence represented by SEQ ID NO:2.
 25. Theisolated nucleic acid molecule of claim 21, wherein said nucleic acidsequence encodes a protein comprising an amino acid sequence comprisingamino acids 134-285 of SEQ ID NO:2.
 26. The isolated nucleic acidmolecule of claim 21, wherein said nucleic acid sequence comprises atleast 390 contiguous nucleotides of SEQ ID NO:1.
 27. The isolatednucleic acid molecule of claim 21, wherein said nucleic acid sequencehybridizes under low stringency conditions to the complement of SEQ IDNO:1.
 28. The isolated nucleic acid molecule of claim 21, wherein saidnucleic acid sequence hybridizes under moderate stringency conditions tothe complement of SEQ ID NO:1.
 29. The isolated nucleic acid molecule ofclaim 21, wherein said nucleic acid sequence hybridizes under highstringency conditions to the complement of SEQ ID NO:1.
 30. The isolatednucleic acid molecule of claim 21, wherein said nucleic acid sequencecomprises SEQ ID NO:1.
 31. The isolated nucleic acid molecule of claim21, wherein said nucleic acid sequence comprises nucleotides 402 through855 of SEQ ID NO:1.
 32. A recombinant nucleic acid molecule, comprisingan isolated nucleic acid molecule as set forth in claim 21 operativelylinked to a transcription control sequence.
 33. A recombinant cellcomprising an isolated nucleic acid molecule as set forth in claim 21,wherein said cell expresses said recombinant nucleic acid molecule. 34.A recombinant virus, comprising an isolated nucleic acid molecule as setforth in claim
 21. 35. A recombinant nucleic acid molecule comprising anexpression vector operatively linked to a nucleic acid moleculecomprising a nucleic acid sequence encoding a protein having TALL-1biological activity, wherein said protein comprises an amino acidsequence selected from the group consisting of: a. SEQ ID NO:2; and, b.a homologue of SEQ ID NO:2, wherein said homologue comprises an aminoacid sequence selected from the group consisting of: (i) an amino acidsequence that is at least about 40% identical to SEQ ID NO:2 over atleast 175 amino acids of SEQ ID NO:2; and, (ii) an amino acid sequencethat is at least about 40% identical to SEQ ID NO:2 over positions134-285 of SEQ ID NO:2.
 36. A method to produce a TALL-1 protein,comprising culturing an isolated cell to express the recombinant nucleicacid molecule of claim 35, under conditions whereby a TALL-1 proteinencoded by said recombinant nucleic acid molecule is produced.
 37. Anisolated TALL-1 receptor homologue, wherein said homologue comprises anamino acid sequence that is: a. at least about 40% identical to SEQ IDNO:11 over at least 35 amino acids of SEQ ID NO:11; and, b. less than100% identical to an amino acid sequence selected from the groupconsisting of SEQ ID NO:11 and SEQ ID NO:17.
 38. The isolated TALL-1receptor homologue of claim 37, wherein said homologue is at least about65% identical to SEQ ID NO:11.
 39. The isolated TALL-1 receptorhomologue of claim 37, wherein said homologue is at least about 75%identical to SEQ ID NO:11.
 40. The isolated TALL-1 receptor homologue ofclaim 37, wherein said homologue is at least about 90% identical to SEQID NO:11.
 41. The isolated TALL-1 receptor homologue of claim 37,wherein said homologue is less than about 95% identical to said aminoacid sequence selected from the group consisting of SEQ ID NO:11 and SEQID NO:17.
 42. The isolated TALL-1 receptor homologue of claim 37,wherein said homologue is less than about 90% identical to said aminoacid sequence selected from the group consisting of SEQ ID NO:11 and SEQID NO:17.
 43. The isolated TALL-1 receptor homologue of claim 37,wherein said homologue is encoded by a nucleic acid molecule comprisinga nucleic acid sequence that hybridizes under moderate stringencyconditions to the complement of SEQ ID NO:10.
 44. The isolated TALL-1receptor homologue of claim 37, wherein said homologue is encoded by anucleic acid molecule comprising a nucleic acid sequence that hybridizesunder high stringency conditions to the complement of SEQ ID NO:10. 45.The isolated TALL-1 receptor homologue of claim 37, wherein saidhomologue binds to TALL-1.
 46. The isolated TALL-1 receptor homologue ofclaim 37, wherein said homologue is a soluble TALL-1 receptor.
 47. Theisolated TALL-1 receptor homologue of claim 37, wherein said homologueactivates NF-κB in a cell expressing said homologue through a TRAF5,TRAF6, NIK, IKKα and IKKβ dependent pathway.
 48. The isolated TALL-1receptor homologue of claim 37, wherein said homologue costimulates Blymphocyte proliferation in a B lymphocyte expressing said homologue.49. An isolated nucleic acid molecule comprising a nucleic acid sequenceencoding a TALL-1 receptor homologue, wherein said homologue comprisesan amino acid sequence that is: a. at least about 40% identical to SEQID NO:11 over at least 35 amino acids of SEQ ID NO:11; and, b. less than100% identical to an amino acid sequence selected from the groupconsisting of SEQ ID NO:11 and SEQ ID NO:17.
 50. A compositioncomprising: a. a compound selected from the group consisting of: (i) anisolated TALL-1 protein; (ii) an isolated antibody that selectivelybinds to said TALL-1 protein of (i); (iii) an isolated TALL-1 receptor;and, (iv) an isolated antibody that selectively binds to said TALL-1receptor of (iii); and, b. a pharmaceutically acceptable carrier. 51.The composition of claim 50, wherein said compound is an isolated TALL-1protein.
 52. The composition of claim 51, wherein said isolated TALL-1protein comprises an amino acid sequence selected from the groupconsisting of: a. SEQ ID NO:2; and, b. a homologue of SEQ ID NO:2,wherein said homologue comprises an amino acid sequence selected fromthe group consisting of: (i) an amino acid sequence that is at leastabout 40% identical to SEQ ID NO:2 over at least 175 amino acids of SEQID NO:2; and, (ii) an amino acid sequence that is at least about 40%identical to SEQ ID NO:20 over positions 134-285 of SEQ ID NO:2.
 53. Thecomposition of claim 51, wherein said isolated TALL-1 protein is encodedby a nucleic acid sequence that hybridizes under moderate stringencyconditions to the complement of a nucleic acid sequence encoding SEQ IDNO:2.
 54. The composition of claim 51, wherein said isolated TALL-1protein comprises an amino acid sequence represented by SEQ ID NO:2. 55.The composition of claim 50, wherein said compound is an isolatedantibody that selectively binds to said TALL-1 protein of (i).
 56. Thecomposition of claim 50, wherein said compound is an isolated TALL-1receptor.
 57. The composition of claim 56, wherein said receptor is asoluble TALL-1 receptor.
 58. The composition of claim 56, wherein saidisolated TALL-1 receptor comprises an amino acid sequence selected fromthe group consisting of: a. SEQ ID NO:11; and, b. a TALL-1 receptorhomologue comprising an amino acid sequence that is: (i) at least about40% identical to SEQ ID NO:11 over at least 35 amino acids of SEQ IDNO:11; and, (ii) less than 100% identical to an amino acid sequenceselected from the group consisting of SEQ ID NO:11 and SEQ ID NO:17. 59.The composition of claim 50, wherein said compound is an isolatedantibody that selectively binds to said TALL-1 receptor of (iii).
 60. Amethod to activate a TALL-1 receptor, comprising contacting a TALL-1receptor with a TALL-1 protein.
 61. The method of claim 60, wherein saidTALL-1 protein comprises an amino acid sequence selected from the groupconsisting of: a. SEQ ID NO:2; and, b. a homologue of SEQ ID NO:2,wherein said homologue comprises an amino acid sequence selected fromthe group consisting of: (i) an amino acid sequence that is at leastabout 40% identical to SEQ ID NO:2 over at least 175 amino acids of SEQID NO:2; and, (ii) an amino acid sequence that is at least about 40%identical to SEQ ID NO:2 over positions 134-285 of SEQ ID NO:2.
 62. Amethod to regulate B lymphocyte proliferation, activation, and/orsurvival, comprising regulating the biological activity of a TALL-1receptor expressed by a B lymphocyte.
 63. The method of claim 62,wherein said step of regulating comprises inhibiting the biologicalactivity of said TALL-1 receptor.
 64. The method of claim 62, whereinsaid step of regulating comprises inhibiting the interaction of TALL-1with said TALL-1 receptor.
 65. The method of claim 64, wherein said stepof inhibiting comprises contacting TALL-1 expressed by a monocyte ormacrophage with a compound that inhibits binding of said TALL-1 to saidTALL-1 receptor.
 66. The method of claim 65, wherein said compound isselected from the group consisting of: a. an antibody that selectivelybinds to TALL-1 and inhibits the binding of TALL-1 to said TALL-1receptor; b. a soluble TALL-1 receptor; and, c. a TALL-1 receptorhomologue, wherein said homologue comprises an amino acid sequence thatis at least about 40% identical over at least 35 amino acids to SEQ IDNO:11, wherein said homologue binds to TALL-1, and wherein said receptordoes not activate NF-κB when expressed by a cell.
 67. The method ofclaim 65, wherein said compound is a soluble TALL-1 receptor.
 68. Themethod of claim 64, wherein said step of inhibiting comprises contactingsaid TALL-1 receptor with a compound that inhibits the interaction ofTALL-1 with said TALL-1 receptor.
 69. The method of claim 68, whereinsaid compound is selected from the group consisting of: a. an antibodythat selectively binds to said TALL-1 receptor and inhibits the bindingof said TALL-1 receptor by TALL-1; and, b. a TALL-1 homologue, whereinsaid homologue comprises an amino acid sequence selected from the groupconsisting of: (i) an amino acid sequence that is at least about 40%identical to SEQ ID NO:2 over at least 175 amino acids of SEQ ID NO:2;and, (ii) an amino acid sequence that is at least about 40% identical toto SEQ ID NO:2 over positions 134-285 of SEQ ID NO:2; wherein saidhomologue binds to said TALL-1 receptor but does not activate saidTALL-1 receptor.
 70. The method of claim 62, wherein said step ofregulating comprises stimulating the biological activity of said TALL-1receptor.
 71. The method of claim 70, wherein said method comprisescontacting said TALL-1 receptor with a compound that increases TALL-1receptor activity.
 72. The method of claim 71, wherein said compound isselected from the group consisting of: a. an isolated TALL-1 protein;and, b. an antibody that selectively binds to said TALL-1 receptor andactivates said receptor.
 73. The method of claim 72, wherein saidisolated TALL-1 protein comprises an amino acid sequence selected fromthe group consisting of: a. SEQ ID NO:2; and, b. a homologue of SEQ IDNO:2, wherein said homologue comprises an amino acid sequence selectedfrom the group consisting of: (i) an amino acid sequence that is atleast about 40% identical to SEQ ID NO:2 over at least 175 amino acidsof SEQ ID NO:2; and, (ii) an amino acid sequence that is at least about40% identical to SEQ ID NO:2 over positions 134-285 of SEQ ID NO:2. 74.The method of claim 62, wherein regulation of B lymphocyteproliferation, activation and/or survival by said method is effective toregulate a B-lymphocyte immune response in an animal.
 75. The method ofclaim 62, wherein inhibition of B lymphocyte proliferation, activationand/or survival by said method is effective to inhibit a Blymphocyte-associated autoimmune disease.
 76. A method to inhibit a Blymphocyte immune response in a patient, comprising inhibiting theinteraction of TALL-1 with a TALL-1 receptor in said patient.
 77. Amethod to inhibit a B lymphocyte-associated autoimmune disease in apatient, comprising inhibiting the interaction of TALL-1 with a TALL-1receptor in said patient.
 78. A method to identify compounds thatregulate the interaction between TALL-1 and a TALL-1 receptor,comprising: a. contacting a TALL-i receptor with a putative regulatorycompound; b. contacting said TALL-1 receptor with a TALL-1 proteincomprising an amino acid sequence selected from the group consisting of:(i) SEQ ID NO:2; and, (ii) a homologue of SEQ ID NO:2, wherein saidhomologue comprises an amino acid sequence selected from the groupconsisting of: (1) an amino acid sequence that is at least about 40%identical to SEQ ID NO:2 over at least 175 amino acids of SEQ ID NO:2;and, (2) an amino acid sequence that is at least about 40% identical toSEQ ID NO:2 over positions 134-285 of SEQ ID NO:2 or a homologue ofTALL-1; wherein said TALL-1 protein binds to and activates said TALL-1receptor in the absence of said putative regulatory compound; and, c.detecting whether said putative regulatory compound regulates saidTALL-1 receptor.
 79. The method of claim 78, wherein said step ofdetecting comprises detecting whether said putative regulatory compoundinhibits the binding of said TALL-1 protein to said TALL-1 receptor. 80.The method of claim 78, wherein said step of detecting comprisesdetecting whether said putative regulatory compound inhibits theactivation of said TALL-1 receptor as compared to in the absence of saidputative regulatory compound.